Abstracts From the Pulmonary Pathology Society 2015 Biennial Meeting

Context: Thirty percent of sporadic lung adenocarcinomas harbor liver kinase B1 (LKB1) mutations, the tumor suppressor gene mutated in Peutz-Jeghers syndrome, a cancer-predisposing condition. LKB1 protein expression and correlation with clinical and tumor characteristics have not previously been studied in lung carcinoma.

Design: Of 85 primary lung adenocarcinomas diagnosed in a 21-month period, 39 (45%) were subjected to LKB1 staining by immunohistochemistry by using the 2011 IASLC/ATS/ERS histologic classification of lung adenocarcinomas. By using normal respiratory epithelium as an internal control, staining was graded as negative, 0; mild, 1; moderate, 2; and strong, 3. Demographic, histologic, and molecular variables were correlated and statistically analyzed.

Results: Nineteen women and 20 men with a mean age of 65 years (range, 32–82 years) were included. One tumor was in situ adenocarcinoma and the remainder were invasive adenocarcinomas as follows: acinar predominant (29); invasive mucinous adenocarcinoma (5); poorly differentiated (1); mixed (2); and solid (1). Cytologic grading was grade 1 (8), 2 (22), and 3 (9). Seventeen tumors harbored KRAS and 4 had EGFR mutations. Loss of LKB1 expression was seen in 16 cases (41%), more frequently in the mucinous subtype than other subtypes (80% versus 38%, respectively; P < .001). Interestingly, 35% of KRAS-mutated tumors showed loss of LKB1 expression; no statistically significant difference was noted with EGFR mutations.

Conclusions: Our preliminary results show loss of LKB1 protein expression in a subset of lung adenocarcinomas. Further studies are warranted and being performed to determine possible prognostic implication of LKB1 protein loss. Furthermore, since invasive mucinous adenocarcinomas have a high association with KRAS mutation, loss of LKB1 protein and KRAS mutation may be related events.

Metastatic pulmonary calcification is characterized by the deposition of calcium within the walls of airways, blood vessels, and alveolar septa. We describe a case of intraalveolar metastatic calcification associated with chronic eosinophilic pneumonia, which to our knowledge has not been reported. A 25-year-old woman with a history of asthma and intravenous drug abuse developed severe shortness of breath and diffuse centrilobular ground-glass opacities on computed tomography of the chest. Video-assisted thoracoscopic lung biopsy disclosed a pattern of organizing pneumonia with patchy airspace fibrin and focally prominent eosinophils. Many of the intraalveolar fibromyxoid plugs were invested with calcific deposits, some of which exhibited an associated giant cell reaction. No exogenous foreign material was identified. Concomitantly, the patient developed hypercalcemia secondary to transient acute renal failure of undetermined etiology and was also found to have leukocytosis with peripheral eosinophilia. The lung biopsy findings were interpreted as most consistent with chronic eosinophilic pneumonia with an unusual pattern of concurrent metastatic pulmonary calcification. In 3 months of follow-up, the patient has responded only marginally to corticosteroids. In addition to airway, vascular, and alveolar septal deposition, metastatic pulmonary calcification can occur within airspaces in association with chronic eosinophilic pneumonia. Patients showing chronic eosinophilic pneumonia with associated intraalveolar calcification on lung biopsy should be examined for hypercalcemia.

Context: Micropapillary (MP) lung adenocarcinoma (LA) has a poor prognosis and low concordance rates in subtyping. The aim of this study was to identify salient MP LA features to enhance its recognition and concordance.

Design: A search of LAs with predominant patterns based on the IASLC/ATS/ERS classification was conducted. Primary, secondary, and additional patterns were recorded in 5% increments. Features associated with MP patterns (eg, tufts and nuclear grade) were compared against other patterns.

Results: Of 29 cases, MP was the predominant (50%), secondary (5%–40%), and minor pattern in 3, 11, and 8 cases, respectively (n = 22; 76% of total cases). Other predominant patterns included lepidic (2 cases), acinar (14), papillary (3), and solid (7). The most common patterns to occur with MP were acinar (68%) followed by papillary, solid, and lepidic. Upon reviewing, single cells and hobnail features (HFs) were noted in MP LAs. When MP coexisted with acinar pattern, the acini consistently showed HFs and abundant high-nuclear-grade single cells, similar to those comprising MP tufts. These were absent in solid and lepidic-predominant patterns and evident in only 1 of 3 papillary LAs (33%). Similar features occurred in the absence of MP histology in only 1 case of mixed solid and acinar patterns (1 of 7; 14%).

Conclusions: This study identifies previously undescribed features of MP LAs' HFs progressing to abundant high-nuclear-grade single cells and tufts, especially in the setting of acinar-predominant LAs. This previously unreported association may result in less interobserver variability, greater MP subtype recognition, better correlation with prognosis, and less mistyping as papillary pattern.

Context: The understanding of pulmonary hypertension has been focused on binomial model for injuries and dysfunctions of endothelial and muscular vascular layer. However, recent studies have shown that the vascular adventitia and myofibroblast may act as biological processing center and critical regulator of vascular remodeling. Our aim is to investigate the role of myofibroblast activation in adventitial pulmonary remodeling.

Design: Wister male rats were sacrificed 21 days after treatment with monocrotaline (MCT; n = 5) compared to controls (CTR; n = 5). Right ventricular pressure; H&E and picrosirius red staining; immunohistochemistry for IL-17–related markers; and in situ immunofluorescence for SMA and collagen types I and V, electron microscopy, and fibronexus morphometry were performed.

Results: The right ventricular pressure and right cardiac hypertrophy index were significantly higher in the MCT group than the CTR group (P < .05). By morphometry, adventitial thickness to <50-μm diameter vessels increased 9 times and total collagen increased 20% in MCT compared to CTR group (P < .001). Collagen I increased 3 times in adventitia of MCT <50-μm vessels compared to CTR, and collagen V, 4 times (P < .001). The SMA+ cell expression in the MCT group was 2 times greater than that of CTR (P < .01). Plasmatic membrane of microfibroblast showed 4 times more fibronexus in the MCT group than the CTR group (P < .003). IL-17, IL-6, and TNF showed overexpression in adventitial environment (P < .001).

Conclusions: SMA expression and fibronexus, an ultrastructural feature and gold standard for myofibroblast, indicate that myofibroblastic activation is turned on in adventitial pulmonary remodeling, which induces collagen V overexpression, an immunogenic collagen, in a Th-17–related environmental manner.

Malignant mesothelioma is a highly fatal cancer of the visceral and parietal pleura most often caused by asbestos exposure. Studies have shown that a fibrous zeolite mineral found in soil, erionite, is a strong causative agent of malignant mesothelioma as well. Cases of erionite-associated pleural mesothelioma have been widely reported in Turkey, but only rarely in North America. Here we report an additional North American case of epithelial malignant pleural mesothelioma in a vehicle repairman who was raised on a farm in the Mexican Volcanic Belt region. A left decortication was performed and lung tissue sections were stained for various markers of mesothelioma and other cancers. Fiber analysis was performed on lung tissue by using analytic scanning electron microscopy (SEM). Histologic examination confirmed malignant pleural mesothelioma. By SEM, there were 53 700 uncoated fibers per gram of wet lung. Energy dispersive spectrometry demonstrated composition of the fibers as erionite. Erionite was also identified in soil samples (by powder x-ray diffraction, electron diffraction, polarized light microscopy, and EM) obtained from the farm in Mexico where the patient was raised. We describe a case of erionite-associated malignant pleural mesothelioma, proven by lung digestion studies and fiber composition analysis. No asbestos fibers in excess of background were found in the patient's lung. Erionite is found in widespread regions of North America, and several cases of mesothelioma have now been identified in association with erionite in central regions of Mexico. Health care professionals should be alert to the possibility of erionite-associated mesothelioma related to environmental exposures.

Dr Roggli consults with plaintiff and defense attorneys in asbestos litigation; Dr Oury does medical legal consulting for asbestos-related cases.

Context: Pulmonary abnormalities in patients with neurofibromatosis type 1 (NF-1) are only sparsely reported and the literature is mainly based on clinical and radiographic findings. Although vascular changes have been reported in association with NF-1, vascular abnormalities in the lung are not well documented. Moreover, pulmonary fibrosis associated with NF-1 has been debated. We reviewed the histologic features in the lungs from patients with NF-1 who underwent autopsy.

Design: Institutional autopsy files (1995–2014) were searched for NF-1. One case was excluded owing to concurrent hemoglobin S–β thalassemia. Hematoxylin-eosin and Movat pentachrome–stained sections of both lungs were reviewed by 2 pulmonary pathologists. Histopathologic features were recorded.

Results: Eight patients (3 men) with NF-1 died at a median age of 53.5 years (range, 33–79 years) from sepsis (n = 3), air embolism, pulmonary hypertension (PHT), dilated cardiomyopathy, massive internal hemorrhage, and malignant peripheral nerve sheath tumor (n = 1, each). Two patients had clinically documented PHT. Five of 8 patients (62.5%) had histopathologic changes of the pulmonary vasculature, including pulmonary arterial changes (n = 4; intimal thickening, thromboembolic lesions, medial hypertrophy), pulmonary venous changes (n = 5; intimal thickening, patchy perivenular chronic inflammation), and capillary proliferation (n = 2). Chronic bronchiolitis (n = 3), minimal to mild emphysema (n = 4), acute bronchopneumonia (n = 2), malignant peripheral nerve sheath tumor (n = 2), silicotic nodules (n = 1), and subpleural fibroelastosis (n = 1) were also observed.

Conclusions: Pulmonary vascular changes were the most prevalent pathologic finding in the lungs of patients with NF-1. No significant cellular or fibrosing interstitial lung disease was identified.

Context: In adenoid cystic carcinoma (ACC) of the head and neck, a t(6;9)(q22-23;p23-24) translocation that results in a fusion of the MYB oncogene and the transcription factor gene NFIB has been demonstrated. The MYB-NFIB fusion oncoprotein activates transcription of MYB-mediated pathways that impact cell cycle control, DNA repair, and apoptosis. This translocation appears highly specific for ACC. Moreover, therapies targeting MYB or MYB-activated pathways to treat ACC are being explored. Pulmonary ACC (PACC) has not been studied for rearrangements of the MYB gene.

Design: Institutional files (1972–2011) were searched for PACC. All cases were re-reviewed and classified according to the predominant histologic pattern (cribriform, solid, tubular). Fluorescence in situ hybridization (FISH) was used with a break-apart strategy to detect MYB rearrangement (at 6q23.3). Medical records were studied.

Results: Forty cases of PACC were studied. Tissue blocks for FISH studies were available in 35 cases. Disruption of the MYB gene region was observed in 12 cases (41%); 17 (59%) showed no evidence of rearrangement. Six cases failed to hybridize. FISH studies performed on other histologic subtypes of lung cancer (10 squamous cell carcinomas, 10 adenocarcinomas, and 10 small cell carcinomas) failed to show MYB rearrangement. There was no significant difference in MYB rearrangement status with respect to predominant histologic pattern, clinical features, or outcome.

Conclusions: Forty-one percent of PACCs harbor a MYB rearrangement. FISH studies for MYB may be of diagnostic utility in PACC, particularly on small biopsy specimens. MYB rearrangement in PACC did not appear to be associated with clinical features or prognosis.

Context: Epstein-Barr virus (EBV)–associated thymic carcinomas (TCas), considered a subset of lymphoepithelioma-like carcinomas (LELCs), usually have a poor prognosis. Because their chemotherapeutic protocol differs from that of other TCas, their distinction is important. We reviewed our TCa cases to identify morphologic, immunophenotypic, and clinical features that might prompt this diagnostic consideration.

Design: Medical records and slides from patients treated for TCa at Mayo Clinic (1953–2014) were reviewed. Tumors, classified according to the World Health Organization and staged by using TNM, were stained with CK5/6 and/or p40 antibodies. EBV-encoded DNA was detected by in situ hybridization.

Results: Clinical, morphologic, and immunohistochemical features of 37 patients with TCa are summarized in the Table. Four TCas (10.8%), including 2 (of 3) EBV+ TCas, morphologically resembled LELC of the head and neck although overall the lymphocytic infiltrate appeared smaller. EBV+ TCas were moderate (n = 1) or poorly (n = 2) differentiated. All patients underwent surgical resection, and neoadjuvant and/or adjuvant therapy.

Conclusions: From our limited data set, young age and large TCa with squamous phenotype and moderate lymphocytic infiltrate should raise suspicion for EBV positivity.

Context: Recreational drug use is known to cause select histopathologic findings in the lungs. Systemic changes may also be seen in the lungs. There is a paucity of large cohort studies assessing histopathologic findings in the lungs of decedents who abused illicit drugs, prescription drugs, and/or alcohol.

Design: We queried institutional autopsy files (1998–2014) for cases with a history of substance abuse (illicit, prescription, and/or alcohol) and/or positive postmortem toxicologic studies. We performed a retrospective review of histologic findings in lungs of these autopsy cases. Histologic findings of the interstitium, vasculature, airways, and pleura were recorded. Autopsy reports, and toxicology and clinical records were reviewed. Frequencies of drug categories and histology were compared by using Fisher exact tests.

Results: Seventy-three autopsy cases (50 men with a median age of 45 years) were reviewed. Drug overdose/toxicity was the most common cause of death (53%) followed by blunt force trauma (10%). The most common histologic findings included pigmented macrophages (63%), smoking-related changes (56%), interstitial changes (40%), small airways changes (32%), and acute lung injury (22%). Associations included granulomas with fentanyl toxicity (P = .03) (predominantly nonnecrotizing), pigmented macrophages with positive urine THC result (P = .01), and marijuana abuse history (P = .01) (predominantly coarse, brown pigment), and with stimulant abuse history (P = .03) (generally “crunchy” brown pigment), and smoking-related changes with positive urine THC result (P = .02) and stimulant abuse history (P = .01).

Conclusions: The identification of such histopathologic findings can help to identify previously unknown drug abuse and/or support a known clinical history of abuse in autopsy cases as well as in the surgical pathology setting.

Context: c-Met is a receptor tyrosine kinase that is overexpressed in malignant pleural mesothelioma (MPM). MET mutations have been identified in 3% to 16% of MPMs; MET amplification has not been reported. We studied c-Met expression and MET amplification in MPM and correlated the results with morphologic and clinical features.

Design: MPMs identified from surgical pathology files (1987–2014) were reviewed and c-Met immunohistochemistry was performed. Staining intensity (0–3) and distribution (0%–100%) were recorded and multiplied (H-score). Staining localization (cytoplasmic and/or membranous) was noted. Fluorescence in situ hybridization was performed with probes for MET and centromere 7. Medical records were reviewed.

Results: Forty-two patients (median age, 69.5 years; range, 41–87 years) had epithelioid (n = 21) or sarcomatoid (n = 21) MPM. Forty patients died, 38 of disease (2 were lost to follow-up). c-Met staining intensity and c-Met H-score were significantly higher in epithelioid than sarcomatoid MPM (P = .002, respectively). Epithelioid MPM showed a predominance of both cytoplasmic and membranous staining (90.5%), compared to sarcomatoid MPM (60%) (P = .03). Stronger staining intensity correlated with increased survival only among patients who did not receive chemotherapy (n = 26; P = .02). While MET amplification was not identified in any MPM (9 epithelioid, 8 sarcomatoid), MET duplication was seen in 1 epithelioid MPM. Chromosome 7 aneusomy was observed in 11 of 17 MPMs (64.7%), which was associated with a trend toward decreased survival (P = .09).

Conclusions: Strong c-Met expression correlates with epithelioid histology in MPM. Strong c-Met expression is only predictive of survival in a subset of patients (patients without chemotherapy). Studies to correlate c-Met expression with treatment response to tyrosine kinase inhibitors are needed.

Context: Although the role of endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) in pulmonary sarcoidosis has previously been investigated, the determining factors in diagnosing sarcoidosis by EBUS-TBNA without rapid on-site evaluation (ROSE) are unclear.

Design: Patients with clinically and radiographically suspected sarcoidosis underwent EBUS-TBNA without ROSE in a prospective study. Presence of noncaseating epithelioid cell granulomas was pathologic evidence of sarcoidosis.

Results: The EBUS-TBNA was performed in 135 patients, 97 of whom had confirmed sarcoidosis. For the patients with sarcoidosis (59 stage I, 42 stage II), EBUS-TBNA provided sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 95.3%, 100%, 98.6%, 76.23%, and 97.18%, respectively, in the diagnosis of sarcoidosis. Diagnostic yield of EBUS-TBNA for sarcoidosis was associated with disease stage, but not associated with serum angiotensin converting enzyme level, number of lymph node stations sampled per patient, or total number of passes performed per patient. At EBUS-TBNA, 253 mediastinal and hilar lymph nodes were aspirated in 135 patients. Multivariate logistic regression revealed that short-axis diameter and more than 1 needle pass per lymph node were independent risk factors associated with positive pathology. No major procedure-related complications were observed.

Conclusions: Endobronchial ultrasound-guided transbronchial needle aspiration is a safe procedure with high sensitivity for diagnosing sarcoidosis, having a higher diagnostic yield in stage I than stage II. To obtain a higher diagnostic yield of EBUS-TBNA in pulmonary sarcoidosis without ROSE, operators should select the largest mediastinal or hilar lymph node accessible and puncture with 2 to 6 passes.

Context: A recent study found that 10% of necrotizing granulomas are idiopathic. We aimed to study the rate of stain-negative and culture-negative necrotizing granulomas within an urban population.

Design: Fifty-nine granulomas resected at an urban university center from 2003–2014 were reviewed retrospectively. Cases were examined for the presence of organisms on fungal and/or acid-fast bacilli stains, and histologic diagnosis of organism. Patient demographics, culture results, clinical history, and follow-up were gathered from electronic medical records. After incorporation of clinical information, cases were classified as either idiopathic, infectious, sarcoid, or autoimmune related.

Results: Forty-three cases (73%) were necrotizing, of which 33% revealed organisms on staining (versus 0% of nonnecrotizing granulomas; P = .06). After incorporation of clinical information, 51% of necrotizing granulomas remained idiopathic. Forty-four percent of necrotizing granulomas and 6% of nonnecrotizing granulomas were due to infection. The most common infectious organisms included Histoplasma (n = 4), nontuberculous mycobacteria (n = 4), Coccidioides (n = 2), Candida (n = 2), and Aspergillus (n = 2). Mycobacterium tuberculosis was present in 1 case. Idiopathic cases were less likely to have presented with respiratory symptoms (P = .01), and were more likely to be single (P = .2). Of idiopathic cases, 3 showed stable nodules on imaging, 3 remained of questionable significance at last follow-up, and 16 had no additional pulmonary symptoms.

Conclusions: In our series, idiopathic granulomas represented a higher proportion than in the previous study; the reason for this is unclear. Our study shows that nontuberculous mycobacteria and Histoplasma species are the most common infectious organisms isolated from necrotizing granulomas; Mycobacterium tuberculosis is a rare finding.

Context: Mesothelial cells are rarely encountered in transbronchial lung biopsies, and the rate of their occurrence in biopsies of transplanted lungs is unknown.

Design: We identified a case of reactive mesothelial hyperplasia in a lung transplant biopsy that caused diagnostic difficulty. Immunohistochemical staining confirmed the nature of the cells as mesothelial (calretinin positive, cytokeratin 7 positive, negative for B72.3). In a series of 816 subsequent biopsies, we prospectively reviewed all tissue fragments and performed immunohistochemical staining on 10 cases that suggested the possibility of mesothelial cells.

Results: A total of 5 cases were confirmed with mesothelial cells; all were surveillance biopsies without evidence of rejection (3 women, 2 men). In 2 cases, including the index case, there were reactive mesothelial cells forming tubular and papillary structures, and in 2 cases there were bland strips of mesothelial cells without reactive features. Communication with the pulmonologist revealed no case with pneumothorax post procedure.

Conclusions: Mesothelial cells indicative of visceral pleural biopsy are present in a small proportion (0.6% in the current series) of lung transplant biopsies and are of no clinical significance.

We present the case of a 64-year-old man with a 9-month history of chronic persistent cough, weight loss, and chills. Coughing episodes were notable for aspiration, loss of consciousness, and occasional blood-tinged sputum production. His history was significant for smoking, several trips to Guatemala, and ownership of an assisted living facility. Review of computed tomography imaging of the chest showed multiple ground-glass opacities of progressively increasing size and number, concerning for adenocarcinoma in situ, per outside hospital report. Wedge resection of the left lung lobes revealed extensive intraalveolar hemorrhage, patchy capillary proliferation, and alveolar septae secondarily expanded by capillary proliferation. Expert outside consultation with utilization of elastic stain confirmed the diagnosis of pulmonary capillary hemangiomatosis (PCH). Internal re-review of the original imaging, as well as reimaging, noted pulmonary hypertension and persistent ground-glass opacities, consistent with a noninfectious etiology and included PCH within the differential diagnosis. This case illustrates an uncommon pulmonary disorder associated with a poor prognosis that is often difficult to differentiate from other pulmonary vascular disorders, such as primary pulmonary hypertension and pulmonary venoocclusive disease, and highlights the varied clinical presentation of PCH. Unlike many cases of PCH, this patient did not present with a prominent clinical history of pulmonary hypertension, dyspnea, or hemoptysis and had many confounding factors in his clinical presentation. The diagnosis of PCH should remain in the differential diagnosis for cases showing histologic features of chronic hemorrhage and pulmonary hypertension. Furthermore, incorporation and re-review of radiologic imaging is an important step in verifying a diagnosis of PCH.

Extracardiac adult rhabdomyomas are rare benign neoplasms showing skeletal muscle differentiation that almost always arise in the head or neck. These tumors have not been reported previously in the lung. We present a case of primary pulmonary rhabdomyoma of adult type in a 53-year-old man with a history of emphysema and heavy smoking who underwent wedge resection of a 2.7-cm round mass in the periphery of the left upper lobe. Grossly, the tumor was well circumscribed, with a pushing border and a pink and somewhat friable cut surface. Microscopically, the neoplasm was also well circumscribed, showing tightly packed, large polygonal cells with eosinophilic, finely granular cytoplasm with central zones of eosinophilia with peripheral cytoplasmic vacuolization (so-called spider cells), associated with a thin-walled vascular network. Necrosis was absent. In some areas, nuclear atypia was striking but appeared degenerative in nature, as mitotic activity was also absent. Immunohistochemistry showed patchy immunoreactivity for desmin and MyoD1, without staining for myogenin, fast myosin, smooth muscle actin, muscle-specific actin, CD34, CD31, S100 protein, HMB-45, Melan-A, or cytokeratins. This immunoprofile indicates myogenic differentiation, and, taken together with the characteristic morphology, supports a diagnosis of primary pulmonary rhabdomyoma of adult type. To our knowledge, this is the first report of extracardiac adult rhabdomyoma arising in the lung. Although primary skeletal muscle proliferations are quite rare in this organ, this case suggests that true rhabdomyomas may occur in very rare instances, and these tumors should be included in the differential diagnosis of eosinophilic epithelioid neoplasms in the lung.

Context: Emergent diseases, such as tuberculosis and histoplasmosis, are characterized by necrotizing granulomatosis (NG). Orphan diseases are sarcoidosis and hypersensitivity pneumonitis (HP), characterized by nonnecrotizing granulomatosis (NNG). Despite a histologic examination and assessments of special stains, a significant proportion of NG cases will appear infectious with no obvious infectious etiology.

Design: Immune response and remodeling of the microenvironment were evaluated in open lung biopsies from 128 patients (71 males, mean age 50 years; 57 females, mean 52 years). Immunofluorescence, immunohistochemistry, morphometry, and real-time polymerase chain reaction (PCR) were used to evaluate the amount of collagen I and III, immune cells, and infectious agents (virus, fungus, and mycobacteria).

Results: Infectious etiology was confirmed in 34 cases (26%), sarcoidosis in 14 (11%), HP in 22 (17%), NG in 46 (36%), and NNG in 14 (11%) after clinical/pathologic/serologic correlation. Ziehl and Grocott staining were negative in 99 cases (77%). A significant increased expression of IL-6, MMP-9, and TGF-β was found in granulomas when compared with normal tissue (8.24 versus 2.48, 21.78 versus 3.70, 19.42 versus 3.53, respectively; P <.001). NNG of sarcoidosis and HP presented significant higher percentage of IL-13 and IL-4 than NG of tuberculosis and histoplasmosis (209.12 versus 85.65 and 129.47 versus 8.76). A similar amount of IL-6, MMP-9, TGF-β, and collagen I and III was found in NNG and NG. Among the 60 granulomas with negative staining for microorganisms, unexplained etiology remained in 22 cases (37%) after PCR.

Conclusions: A similar pathway of granuloma immunity and remodeling was found in orphan and emergent granulomatous diseases on the basis of etiologic agents.

Context: Collagen V (COLV) is normally sequestered within the lung interstitium and therefore hidden from the immune system, being considered an autoantigen involved in experimental and human pulmonary fibrosis. Previous studies have suggested a possible contribution of IL-17 in the development and progression of pulmonary inflammation and fibrosis. Our aim was to correlate IL-17+ cells and pulmonary fibrosis in C57BL/6 mice immunized with COLV.

Design: C57BL/6 female mice (n = 6) were subcutaneously immunized (IM) with 150 μg/200 μL of COLV in complete Freund adjuvant. Control mice (n = 6) were immunized with adjuvant. Collagen deposition was evaluated by picrosirius, immunofluorescence, and quantified by image analysis. TGF, CTGF, CD4+, and IL-17+ cells were evaluated by immunohistochemistry and point counting method.

Results: C57BL/6 IM mice presented with intense pulmonary inflammation with significant numbers of CD4+ (P = .002) and IL-17+ (P = .001) cells in the pulmonary interstitium, prominent thickness of the septal and bronchovascular interstitium with thick collagen fibers and higher amounts of type I (P < .005) collagen, compared to controls. In addition, C57BL/6 IM mice showed high expression of COLV thick fibers along the bronchovascular and septal interstitium (P = .002), compared to controls. Higher expression of TGF (P < .002) and CTGF (P < .001) were observed in C57BL/6 IM mice than in the control group.

Conclusions: COLV-induced pulmonary remodeling was seen in healthy C57BL/6 mice, suggesting a promising pulmonary fibrosis model important for study of this pathogenesis. Higher expression of IL-17+ cells correlated with pulmonary fibrosis and COLV overexpression, suggesting that this cytokine can play a role in pulmonary remodeling. Strategies to block IL-17+ cells may represent a promising therapeutic target for the pulmonary fibrosis process.

Context: Differential diagnosis may be difficult between pleural malignant mesothelioma (PLMM) and pulmonary adenocarcinoma involving the visceral pleura (PA), and between peritoneal malignant mesothelioma (PEMM) and papillary serous adenocarcinoma of the peritoneum (PSA). To help differentiate PLMM from PA and PEMM from PSA, we used immunohistochemistry to examine claudin 4 and PAX8.

Design: Using formalin-fixed, paraffin-embedded blocks from each case, we compared 23 PLMMs (19 epithelioid type and 4 biphasic type) with 51 PAs, and 22 PEMMs (16 epithelioid and 6 biphasic) with 11 PSAs.

Results: Claudin 4 cellular membranous staining was demonstrated in 51 (100%) and 11 (100%) PAs and PSAs, respectively, whereas among PLMMs and PEMMs it was expressed in only 9% and 5%, respectively. For the differentiation of PLMM from PA, the sensitivity and specificity for claudin 4 were 92% and 97%, respectively. For the differentiation of PSA from PEMM, the corresponding values were 96% and 97%, respectively. PAX8 nuclear positivity was demonstrated in 9 (39%) and 11 (100%) PLMMs and PSAs, respectively, whereas among PAs and PEMMs it was expressed in only 2% and 5%. For the differentiation of PLMM from PA, the sensitivity and specificity for PAX8 were 39% and 98%, respectively. For the differentiation of PSA from PEMM, the corresponding values were 100% and 96%.

Conclusions: Claudin 4 is very useful for distinguishing PLMM from PA, and also PEMM from PSA. Although PAX8 has some validity for differentiating PEMM from PSA, we cannot present the PAX8 value for diagnosis because of low sensitivity in PLMM.

Context: The purpose of our study was to investigate the value of ALK immunohistochemistry (IHC) as a screening tool for EML-ALK rearrangement, as already proposed by several reports, in a considerably large series of patients with lung cancer.

Design: ALK IHC was performed in 1586 lung cancer specimens (1252 adenocarcinomas, 292 NSCLCs, and 42 others) by using the D5F3 rabbit monoclonal antibody and ultrasensitive OptiView DAB IHC Detection Kit with amplification (Ventana anti-ALK, D5F3) and interpreted as negative (no staining), weak (faint incomplete staining), moderate (strong incomplete), or strong (strong complete). For fluorescence in situ hybridization (FISH) analysis, a break-apart probe set (Vysis, Abbott Molecular) was used in 205 cases.

Results: ALK IHC was negative in 1333 specimens (84%); 215 (13.5%) of the cases showed weak to moderate staining, whereas 38 (2.4%) were strongly positive. FISH analysis was performed in 205 specimens (31 strongly positive, 172 weak to moderate, 2 negative). Six of the weakly to moderately stained specimens were FISH positive. Twenty-six of the strongly IHC-positive specimens were also FISH positive, whereas 5 were FISH negative of which 3 responded well to crizotinib therapy.

Conclusions: ALK IHC represents a reliable screening tool. Strong and complete ALK staining could be scored as ALK positive, since IHC appears to be more sensitive than FISH to identify putative responders, especially considering the good response to crizotinib in IHC-positive, FISH-negative cases. In all weakly to moderately stained cases, FISH or other additional studies, such as polymerase chain reaction, are needed.

Context: Birt-Hogg-Dubé syndrome (BHDS) is an inherited disorder caused by genetic mutations of folliculin (FLCN). Individuals with BHDS have multiple pulmonary cysts and skin papules, and they are at high risk for developing renal cell carcinomas. Currently, little is known about whether patients with BHDS are predisposed to develop neoplasms in organs other than the kidney.

Design: In this study, we describe 12 neoplastic pulmonary lesions in 5 patients from our database of 270 patients with BHDS. The histopathologic types of the surgically resected neoplasms included adenocarcinoma in situ (n = 1), papillary adenocarcinoma (n = 1), micropapillary adenocarcinoma (n = 1), atypical adenomatous hyperplasia (n = 8), and micronodular pneumocyte hyperplasia (MPH)–like lesion (n = 1). These lesions were microdissected, and possible somatic events of FLCN were investigated. Immunostaining with mutation-specific antibodies against epidermal growth factor receptor (EGFR) and antibodies against mTOR pathway molecules was also performed.

Results: The 1 MPH-like lesion showed loss of heterozygosity (LOH) of FLCN, whereas none of the adenocarcinomas showed LOH. Two adenocarcinomas were positively immunostained for mutation-specific EGFR. All lesions except the MPH-like lesion were strongly immunostained for phospho-mTOR and phospho-S6.

Conclusions: Individuals with BHDS are at risk for various pulmonary neoplasms of pneumocyte lineage; LOH of FLCN may be related to the development of the MPH-like lesion, whereas further study is necessary to determine whether any cross-talk between activated EGFR and mTOR pathways under the haploinsufficient condition of folliculin may underlie the development of adenocarcinomas.

Context: The MUC5B gene variant is present in 50% to 60% of patients with idiopathic pulmonary fibrosis (IPF). As MUC5B variant is also observed in 20% of patients without IPF, additional factors, such as chronic aspiration, might contribute to IPF pathogenesis. A clinical trial with gastroesophageal reflux therapy demonstrated longer survival in patients with IPF. We encountered a case of classic usual interstitial pneumonia (UIP) morphology but with prominent fibroblast foci (FF) involving the small airways from a patient with severe gastroesophageal reflux disease (GERD). We hypothesized that disrupted mucociliary defense in distal airways caused by chronic aspiration of gastric juice may play a role in pulmonary fibrosis and manifest as prominent FF in small airways.

Design: UIP cases diagnosed by wedge biopsies over a 5-year period were identified from our surgical pathology database. Slides were reviewed by 2 blinded authors and scored 1 to 3 for prominence of FF. Clinical information was obtained.

Results: Forty-nine patients (31 men; ages 42–81 years, median = 65 years) were diagnosed as having UIP. Five to 29 slides per case (median = 10) were reviewed. The right lower lobe was most commonly sampled. Eighteen cases (36.7%) demonstrated prominent airway FF (score 3). Twenty-seven patients (55%) had diagnosis of GERD, and 5 cases had hiatal hernia that was significantly associated with prominent airway-centered FF (P = .05). No association was seen between GERD or the use of protein-pump inhibitors (PPIs) and prominent airway FF.

Conclusions: Prominent airway-centered FF might suggest underlying hiatal hernia in UIP. Although clinical diagnosis of GERD and the use of PPIs did not reveal an association in the present study, larger studies could be helpful.

Context: Epidermal growth factor receptor mutations (EGFRm) in lung adenocarcinomas (ACs) are known to predict responsiveness to tyrosine kinase (TKI) inhibitors, and anaplastic lymphoma kinase rearrangements (ALKre) predict response to ALK inhibitors. In the United States, EGFRm and ALKre occur in 10% and in 2% to 7% of patients, respectively. There has recently been a recommendation to test tumors at diagnosis rather than being based on smoking, histologic pattern, and demographics. We evaluated the molecular testing results in our veteran population for cost-effectiveness and response.

Design: We examined 115 patients with ACs in which the tumor was sent to a reference laboratory for EGFRm testing by polymerase chain reaction and/or ALKre via fluorescence in situ hybridization. The specimen site, molecular testing results, tumor pattern, clinical and demographic features, and outcomes were reviewed.

Results: From 2000 to now, EGFRm was found in 3 of 92 patients (3%; 3 males, 1 nonsmoker). ALKre was found in 2 of 89 patients (2%; 2 males, 1 nonsmoker). All 3 patients with EGFRm could not tolerate TKI inhibitors. One patient with ALKre tolerated continuous crizotinib with no progression in 6 to 12 months (Asian nonsmoking male). EGFRm and ALKre testing cost $137 750.00 and $38 086.66, respectively.

Conclusions: If all ACs had been tested at diagnosis, the cost would have been $2 000 734.00 to detect <2%–3% patients. In veterans, EGFRm and ALKre testing is best used selectively (nonsmokers, Asian ethnicity, and young age) and is not cost-effective in newly diagnosed ACs. In our patients, who are older with comorbidities, TKI inhibitors and crizotinib are poorly tolerated.

Context: It is well known that the initiation, distribution, and severity of fibrosis vary among different chemical injuries. However, the mechanisms of chemical variation and their epithelial/mesenchymal basis, as well as the activation of susceptibility to pulmonary fibrosis by profibrotic signals, are poorly investigated. Because of this, we aimed to evaluate and compare the activation profile and perpetuation of fibrosis induced by bleomycin (BLM) and 3-5-di-tert-4-hydroxytoluene (BHT).

Design: For pulmonary fibrosis, groups of male mice (C57Bl/6; n = 6) had BLM (0.1 U) administered by an intratracheal or intraperitoneal route with BHT (400 mg). Sterile saline or corn oil was used as control. Lungs were removed 14 (early) and 21 (late) days after induction, and analysis was performed. All experimental procedures were performed according to the guidelines of the Ethical Committee of the Faculty of Medicine of University of Sao Paulo, Brazil (process code 372/11).

Results: Higher amounts of collagen, evaluated by hydroxyproline and Masson staining, were found in BLM and BHT groups when compared to controls (P <.001). Upregulation of TGF-b, Smad3, Smad6, IL-1b, Stat 6, End, and VEGF gene expression was found in BLM and BHT groups when compared to controls (P <.05). Interestingly, we observed down-regulation in AGT expression in the late BHT group when compared to control and late BLM (P < .001).

Conclusions: The upregulation of cytokines and growth factors resulted in an increase of total and specific types of lung collagen accumulation in the lungs of BLM and BHT groups. However, distinct mechanisms of peribronchiolar and peripheral fibrosis may be involved, since we found down-regulation of the AGT gene in the late BHT group.

Financial support: FAPESP.

Context: Severe dengue fever includes dengue hemorrhagic fever (DHF) and dengue shock syndrome. Previously, the Ministry of Health of Brazil categorized dengue with complications (DCC) when the patient died without changes in hemostasis.

Design: One hundred twenty-four autopsy cases with fatal dengue, performed between 2011 and 2013 in Ceara, Brazil, were analyzed. Standard staining, immunohistochemistry for dengue antigen, and polymerase chain reaction assay for viral RNA were performed.

Results: Twenty-seven cases were classified as DHF (21.8%), while 97 were DCC (78.2%). The median age was 36.9 years (1–84 years); 65% of patients were men. Most patients died within 1 to 5 days after the onset of dengue symptoms. Underlying diseases were hypertension (39.7%) and diabetes (19.3%). The main symptoms were fever (85%), dyspnea (70%), cough (53%), abdominal pain (57%), and hemorrhagic phenomenon (48%). Histologically, intraalveolar edema, congestion and/or hemorrhage, interstitial or intraalveolar inflammatory cell infiltration, and hyaline membranes were observed in all cases in different degrees of severity. Severity was scored according to the area of the lung involved, defining 3 categories: absent (0); mild, up to 50% (1%–50%) of pulmonary parenchyma compromised; and severe, 51% to 100% of lung parenchyma compromised. According to severity score, intraalveolar edema, pulmonary cell infiltration, and hemorrhage were significantly more severe in the DHF group than DCC group (P < .01). Patients with severe score for interstitial inflammatory cell infiltration had a risk of 13.12 (2.54–67.64) of dying from changes in hemostasis and vascular permeability (P < .01), whereas for those with mild score for edema and hemorrhage, the risk was 3.12 (1.07–9.17) and 4.04 (1.39–11.71), respectively.

Conclusions: Patients with signs of vascular leakage should be monitored for warning signs in order to avoid a fatal outcome.

The frequency of asbestos-related pulmonary fibrosis leading to lung transplant is not well documented. A review of our laboratory information system in the setting of a high bilateral orthotopic lung transplant program (BOLT) at our institution, as well as a PubMed literature search, demonstrates a low frequency of asbestosis-related pulmonary fibrosis resulting in lung transplant, emphasizing that lung transplant due to interstitial fibrosis secondary to severe asbestosis is relatively rare. We present a unique case of a 65-year-old man with a history of interstitial lung disease in a background of asbestos exposure who underwent bilateral lung transplant and was found to have severe asbestosis (grade 4/4). We present radiographic and gross lung findings associated with the disease in addition to histologic findings. We furthermore demonstrate the use of asbestos fiber quantification by light and scanning electron microscopy.

Drs Sporn and Roggli consult with plaintiff and defense attorneys in asbestos litigation.

Pulmonary alveolar proteinosis is an uncommon disease with intraalveolar accumulation of surfactant protein and phospholipids. Only a few variant alveolar proteinosis cases with negative periodic acid–Schiff (PAS) staining have been described; other atypical cases include those with serous lavage fluid, negative anti-GMCSF serology, or steroid responsiveness. A 51-year-old nonsmoking woman with a past medical history of childhood Rocky Mountain spotted fever infection and pseudotumor cerebri presented with a 6-month history of progressive dyspnea. Her pulmonary function tests demonstrated a restrictive pattern and ground-glass opacities, and multiple intraparenchymal cysts were seen on imaging. The differential diagnosis included lymphoid or desquamative interstitial pneumonia and pulmonary alveolar proteinosis. A wedge biopsy was performed, which demonstrated significant intraalveolar eosinophilic material with occasional macrophages without hemosiderin; no small airway disease or inflammatory infiltrate was noted. The findings were consistent with pulmonary alveolar proteinosis; however, a PAS stain failed to highlight the proteinaceous material. Electron microscopy demonstrated lamellar bodies, and a high titer of anti-GMCSF antibody was detected, consistent with a diagnosis of variant alveolar proteinosis. A trial of prednisone failed to improve her restrictive physiology or symptoms. Bilateral bronchoalveolar lavage yielded moderate amounts of foamy proteinaceous material, which was culture negative, with moderate improvement by imaging and significant and durable improvement of her dyspnea. This case of variant alveolar proteinosis is unique in its PAS-negative alveolar material, but is otherwise typical of pulmonary alveolar proteinosis relative to its characteristic lavage fluid, histology, electron microscopy findings, and treatment response.

Birt-Hogg-Dubé syndrome (BHDS) is an inherited disorder caused by genetic mutations of folliculin (FLCN). Individuals with BHDS develop multiple pulmonary cysts, skin papules, and renal cell carcinomas. Although several histopathologic studies of the pulmonary cyst in BHDS have been published, they were mostly based on small peripheral lung specimens. We investigated the pathologic features of cysts in the autopsied lung of an 81-year-old man with BHDS, who died of advanced prostatic carcinoma. He had been diagnosed as having BHDS from a germline mutation of FLCN and pulmonary cysts. Grossly, multiple cysts were distributed in all pulmonary lobes, either subpleurally or deep to the parenchyma, preferentially located in the lower lobes. They tended to be larger toward the lower mediastinal/central side of the lung. Cysts were well demarcated, typically with a slightly irregular football-like or oval shape. They had very thin walls with a smooth and glistening inner surface, and the surrounding parenchyma showed no fibrosis or emphysematous change. Many of the cysts, especially larger ones, were closely associated with bronchovascular bundles, which sometimes protruded into the cystic space. Some large cysts abutted on one another, appearing multilocular-like. Histopathologically, the cysts were lined by a layer of flat alveolar epithelium and frequently incorporated into the stroma of interlobular septa or bronchovascular bundles in part. The pulmonary cyst in BHDS was grossly and histopathologically distinct from conventional bullae/blebs. The nature of the cyst may be a hamartomatous formation of giant alveolus-like structure with interaction between alveolar epithelium and stroma.

Context: The high incidence and mortality rates of lung cancer reflect the need for new diagnostic and prognostic markers capable of early disease detection. We sought to evaluate the diagnostic and prognostic role of sputum cofilin-1 and the relationship between this biomarker with HA and its receptor (CD44) in patients with non–small cell lung cancer (NSCLC).

Design: Cofilin-1 and CD44 were analyzed by ELISA immunoassay and HA by “ELISA-like” fluorometric assay in the sputum of 74 patients with NSCLC, 13 cancer-free patients with obstructive lung disease, and 8 healthy individuals.

Results: Sputum cofilin-1 levels were increased in patients with lung cancer when compared to cancer-free patients (P < .05) and volunteers (P < .05). High expression of sputum cofilin-1 correlated to T4 (P = .01) and M stage (P = .03), tobacco history (P = .01), and squamous cell carcinoma (P = .04). Cancer cell–associated cofilin-1 was an independent predictor of metastases with a high risk when >1475.83 pg/mL. Sputum cofilin-1, at a cutoff value of 248.9 pg/mL, presented sensitivity and specificity of 0.80 and 0.67, respectively, in distinguishing healthy volunteers from patients with NSCLC. Cofilin-1 was also able to distinguish cancer-free patients from cancer patients at a cutoff of 802.5 with sensitivity and specificity of 0.60 and 0.54, respectively.

Conclusions: Cofilin-1 presented sensitivity as a diagnostic biomarker for lung cancer in sputum and was associated with metastases. The association between sputum cofilin-1 and CD44 in cancer patients suggests that during tumor development, high levels of cofilin-1 facilitate tumor growth and the penetration of capillaries into the tissue milieu.

Context: A current diagnostic dilemma in asbestos-exposed subjects with diffuse lung fibrosis is to determine the presence or absence of asbestosis. Asbestosis is a dose response associated with heavy prior asbestos exposure. There is dispute in the literature as to whether subjects with asbestosis show a usual interstitial pneumonia (UIP) pattern.

Design: This is a retrospective analysis of subjects (with radiologically or pathologically suspected pulmonary fibrosis) systematically referred to the United Kingdom Medical Research Council Pneumoconiosis Unit during the period 1969–1985. The source data comprised dockyard workers, asbestos factory workers, gas mask manufacturers, and asbestos textile workers. The total worker population in this cohort is estimated to be 20 000 persons. Routine lung sections were examined by experienced pathologists. Correlative asbestos fiber counts were established by transmission electron microscopy.

Results: A total of 233 cases were reviewed. Usual interstitial pneumonia pattern was observed in 2 of 188 dockyard workers, 1 of 43 asbestos factory workers, and no gas mask or textile factory workers (total, 1.3% cases). This incidence in this cohort's population is 3/20 000 (15/100 000), compared to published incidence of (2–10/100 000). Subjects with diffuse interstitial fibrosis had a fibrotic pattern of nonspecific interstitial pneumonia pattern.

Conclusions: Usual interstitial pneumonia is infrequently observed in historical asbestos-exposed cohorts; the incidence of disease could be accounted for by natural occurrence in the large workforce. Those cases with UIP pattern fibrosis show no dose response pattern, with numbers of asbestos bodies and fibers providing further evidence that UIP is not observed in confirmed cases of asbestosis.

Drs Attanoos and Gibbs provide expert testimony in asbestos cases.

Context: Lung squamous cell carcinoma (SCC) mostly grows as cohesive tumor sheets surrounded by an abundant desmoplastic stroma. Several invasion modes have been described ranging from mesenchymal to coordinated and cohort. Thereby, the feature of tumor budding was particularly prognostic. Such buds represent tangential cuts of sprouting tubules in 3D, thus their number is susceptible to the cut thickness. We implemented a computer-based algorithm for more globally assessing the tumor microarchitecture of lung SCC, using the concept of fragmentation.

Design: Surgically resected tumors from chemonaive patients with lung SCC (test TMA cohort: n = 400, 2 cores per patient; validation whole section cohort: n = 100, 2 blocks per patient) were immunohistochemically stained with pan-cytokeratin. Color-based segmentation was performed with Fiji software. The number of tumor fragments isolated from one other by stroma was counted and correlated with clinicopathologic data including disease-free survival (DFS) and overall survival (OS).

Results: The number of tumor fragments larger than 5 cells ranged from 2 to 72 (median = 8) for the TMA cohort. A high number of tumor fragments positively correlated with blood vessel infiltration (correlation coefficient, 0.171; P < .01) and worse prognosis (OS: HR = 1.45, P < .01). On whole sections, the number of fragments larger than 5 cells ranged from 300 to 9526 (median = 1433). A high number of fragments correlated with decreased DFS and OS (HR = 1.87, P < .05; HR = 1.90, P < .01, respectively).

Conclusions: Fragmentation of lung SCC into discrete elements correlates with aggressiveness and may be useful for TNM staging. The computerized morphometric approach provides quantitative information for the different types of SCC invasion modes.

Context: Patients with lung cancer who are treated with tyrosine kinase inhibitors need to undergo rebiopsy at progression of disease. Obtaining adequate samples can be challenging owing to treatment-related changes, including marked fibrosis and necrosis. We use rapid on-site cytologic evaluation (ROSE) to determine tumor cellularity and triage specimens.

Design: We reviewed our databases from National Cancer Centre of Singapore for patients with adenocarcinoma enrolled in our protocol of Individualized Molecular Profiling for Assigning Clinical Trial to determine the impact of the triage of specimens, based on ROSE, in the success of molecular profiling.

Results: Seventy-two patients had biopsy specimens sent for initial molecular profiling. Two patient samples were insufficient; one of these was bronchoscopically obtained and demonstrated only a few tumor cells by ROSE. One sample was considered of low DNA quality and corresponded to a computerized tomography–guided transthoracic biopsy (computed tomography [CT]-guided TTNA), which had focal low cellularity. Eighty-seven of 112 patient specimens were sent for next-generation sequencing profiling. Two were insufficient and corresponded to a CT-guided TTNA, which yielded a tiny fragmented core with only rare tumor cells and fibrotic stroma. Three of 87 were of low DNA quality. These corresponded to a bronchoscopic biopsy guided by ultrasound (EBUS) with only rare tumor cells seen, a CT-guided TTNA with rare cells seen, and a CT-guided pleural biopsy with no tumor cells seen by ROSE, respectively.

Conclusions: ROSE at the time of rebiopsy is useful for the triage of specimens. It may save resources on unnecessary processing of cytologically insufficient samples.

Context: The PD1/PD-L1 checkpoint inhibitor pathway has recently received great interest in lung cancer owing to the development of specific PD1 or PD-L1 inhibitors that have shown significant clinical activity. Here we aim at determining whether immunohistochemistry (IHC) is a sensitive and reproducible method to detect PD-L1 expression in lung tumors. An additional hypothesis is that tumors expressing PD-L1 are immune-tolerant and hence associated with a more aggressive behavior.

Design: PD-L1 expression was assessed with IHC (Ab clone SP124, Ventana) on archival formalin-fixed, paraffin-embedded surgical tumor specimens, arrayed on TMAs with duplicate 1-mm cores. All patients (n = 263) had early-stage node-negative lung cancer and received curative surgery between 1987 and 2002. Patient and tumor characteristics were as follows: median age (IQR), 67 years (61–73 years); sex, male (56%)/female (44%); histology, squamous cell carcinoma (SCC) (41%)/nonsquamous (N-Sq)-NSCLC (50%)/neuroendocrine (8%); p-stage, IA (49%)/IB (34%)/II (17%). PD-L1 staining was scored as positive if present in >5% of tumor cells, independently of staining intensity.

Results: Membranous PD-L1-positive staining was considered as positive and was seen in both tumor cells and inflammatory cells. PD-L1 was positive in 9% of cases, corresponding to 17% of SCCs, 4% of N-Sq, and 4% of neuroendocrine cases (χ², P < .001). For this reason, additional statistical analysis was restricted to the SCC subgroup (n = 109). PD-L1 expression was not associated with p-stage, but rather with sex (29% versus 12% PD-L1+ cases in females versus males, respectively; P = .03) and age (median age in PD-L1+ versus PD-L1− was 63 versus 71 years, respectively; P = .002). Median overall survival (OS) in SCC was 66 months. No statistically significant association between PD-L1 expression and OS was observed.

Conclusions: PD-L1 was expressed in a minority of lung cancer cases in this series, predominantly in the SCC group. Further staining and analysis will be performed on an additional 300 cases.

Context: Transmission electron microscopy with energy dispersive x-ray spectrometry represents an important tool in the assessment of prior asbestos exposures. Lung digestion analyses are not always available and reliance is then placed on light microscopic observations.

Design: This retrospective study examined the correlation between light microscopic assessments of asbestos bodies and transmission electron microscopic asbestos fiber counts. During a 3-year period (2012–2014), cases studied in our institution (n = 513) were included to analyze the correlation. The results were compared with the 2012 laboratory asbestosis range values established from 236 asbestosis cases and the 2010 control reference range for nonoccupational exposures in 29 individuals.

Results: See Table (next page).

Conclusions: Asbestos body counts directly correlate with commercial amphibole asbestos fiber levels on mineral analysis. There is no observed correlation with chrysotile and tremolite. The failure to detect asbestos bodies by light microscopy correlates with subasbestosis range fiber counts. Asbestos bodies on crocidolite fiber are smaller and are more difficult to detect than are amosite-coated asbestos bodies. The detection of any asbestos body in lung section correlates with elevated fiber counts above control reference ranges.

Drs Attanoos and Gibbs provide expert testimony in asbestos cases.

Context: The cytologic diagnosis of malignant pleural mesothelioma (MPM) is not fully accepted. Fluorescence in situ hybridization (FISH) analysis of p16 gene is helpful for differentiation between malignant and benign mesothelial proliferation. We analyzed the sensitivity of cytologic examination for the diagnosis of MPM.

Design: We reviewed medical records of 37 cases with nonsarcomatoid pleural mesothelioma (28 epithelioid, 9 biphasic) that were diagnosed between 2000 and 2014. We retrospectively analyzed cell blocks of serosal effusions with atypical mesothelial cells and biopsy samples with p16 FISH from 16 patients with nonsarcomatoid mesothelioma (12 epithelioid, 4 biphasic).

Results: Twenty-nine of 37 cases (78%) had a fluid cytology specimen before histologic confirmation. Twelve (41%) received a cytologic diagnosis of positive for malignant mesothelioma, 6 (21%) were suggestive of mesothelioma, and 3 (10%) were designated atypical; 3 (10%) were misclassified as positive for adenocarcinoma, and the remaining 5 (17%) were classified as benign. As a result, 83% of the patients with MPM have atypical cells in cytology samples. Homozygous deletion (HD) of p16 gene was observed both in cell blocks and biopsy samples of 69% (11 of 16) of the patients.

Conclusions: We confirmed that the results of p16 gene FISH on cell blocks is as reliable as on tissue sections. Cytologic diagnosis of mesothelioma with serosal effusions could have been possible in 57% of cases of nonsarcomatoid mesotheliomas. We suggest that confirmation of the mesothelial origin of atypical cells with immunohistochemistry accompanied by analysis of HD of p16 gene is needed for the cytologic diagnosis of mesothelioma.

The association of lymphangioleiomyomatosis (LAM) and tuberous sclerosis in female patients of childbearing age is well known; however, a very few well-documented cases are described in male patients. Furthermore, 2 other interstitial cell proliferation processes similar to LAM have been described in patients with tuberous sclerosis and are referred to as clear cell proliferation and PEComatosis. We present the histologic findings of a 19-year-old man with tuberous sclerosis and recurrent spontaneous pneumothorax, treated with wedge lung resection and pleurodesis. Hematoxylin-eosin–stained sections showed a subpleural lung parenchyma area with enlarged alveolar spaces and interstitial proliferation of predominantly round cell clear cytoplasm; few spindle cells with pale eosinophilic cytoplasm were mixed in some areas. Immunohistochemical staining revealed that the interstitial cells were positive for SMA and PR; a few cells were positive for HMB-45, desmin, and ER; and isolated cells were positive for Melan-A. Results of S100 and CD34 staining were negative. Other areas of the lung sample were normal. In 3 years of follow-up, the patient did not show any clinical or functional evidence of lung involvement. Lung computed tomography scan performed last year had normal findings. The findings of this particular case do not fit with the typical LAM profile because of subtle different distribution of changes as a uniform area of enlarged alveolar spaces. The interstitial proliferative cells are predominantly round with clear cytoplasm and the HMB-45 and Melan positivity is less extensive. It is unknown to us the meaning of these findings relative to the prognosis. The patient is in follow-up.

Context: Cumulative evidence suggests that aerogenous metastasis of lung adenocarcinoma occurs and is underrecognized. Imaging features are helpful in differentiating possible aerogenous spread of tumor from vascular (hematogenous/lymphatic) metastases and from synchronous primary tumors.

Design: Sixteen patients with multiple resected lung adenocarcinomas were identified. Histology slides were reviewed and secondary tumors classified into 3 groups: separate primary tumor (SPT), vascular intrapulmonary metastasis (VIM), and aerogenous intrapulmonary metastasis (AIM) according to an adapted comprehensive histologic assessment that included previously proposed criteria for aerogenous metastasis. Corresponding computed tomography images were blindly reviewed and patients classified according to previously proposed criteria into the same groups.

Results: Histologic assessment revealed 7 AIM, 4 SPT, 1 VIM and 4 inconclusive cases (AIM versus VIM). All primary tumors in histologic AIM cases were associated with extensive airspace disease (mucinous, lepidic, papillary, or micropapillary). Radiologic assessment revealed 6 AIM, 4 SPT, 2 VIM, and 4 inconclusive cases (AIM versus VIM). Among the 7 histologic cases of AIM, radiology identified 5 AIM, 1 AIM versus VIM, and 1VIM. The 4 cases histologically classified as SPT had 100% radiology concordance. The case histologically classified as VIM was inconclusive by radiology, and the 4 histologically inconclusive cases were radiologically classified as inconclusive (n = 2), AIM (n = 1), and VIM (n = 1). The overall distinction between SPT (n = 4) and intrapulmonary metastasis (n = 12) had 100% concordance.

Conclusions: Our study shows good radiologic-pathologic concordance in classifying multiple lung tumors into separate primaries, vascular metastasis, or aerogenous metastasis. These data are in agreement with literature and support the occurrence of aerogenous spread of lung adenocarcinoma.

Carcinoma ex pleomorphic adenoma (CXPA) is a rare neoplasm that represents carcinomatous transformation from the epithelial component of pleomorphic adenoma. It comprises most malignant mixed tumors of the salivary gland. CXPA develops in association with a primary or recurrent benign pleomorphic adenoma. We report a case of CXPA of submandibular gland with metastases to bilateral lungs and cervical lymph nodes. A 71-year-old woman with a past medical history of diabetes, hypertension, and coronary artery disease presented with enlargement of the submandibular gland. Computed tomography scan showed a calcified mass measuring 3.6 cm × 2.5 cm. The mass was resected and diagnosed as CXPA. Four years later, the patient was found to have bilateral pulmonary nodules and enlarged lymph nodes in the left cervical area. A wedge lung resection showed that the tumor was composed of salivary gland–type features characterized by a malignant epithelial/myoepithelial component set in a chondromyxoid stroma. The tumor cells formed an adenoid structure in myxoid stroma. The tumor cells had large hyperchromatic nuclei, prominent nucleoli, and scant cytoplasm. Myxoid mesenchymal stroma and benign pleomorphic adenoma elements were observed in multiple areas. The benign pleomorphic adenoma fields consisted of epithelial cells that formed ducts and nests in chondromyxoid stroma. These findings supported the diagnosis. CXPA is a difficult diagnosis to make, as the benign pleomorphic adenoma component may be small and overlooked and the malignant component may completely replace the benign elements. When recurrence and distant metastasis occur, survival is extremely low; hence, early and adequate removal is critical.

Context: The WHO/IASLC classification of lung adenocarcinoma (LADC) emphasizes the distinction of adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) from their invasive counterparts. Biomarkers of lung invasion in this setting are limited.

Design: Previously published gene expression data from nonmucinous AIS and invasive AdCa (containing nonmucinous lepidic pattern) of various subtypes identified 2 predominant clusters of 340 differentially expressed genes localizing to 4 major regions on 7q. Comparative genomic hybridization and Affy 6.0 SNP array data showed copy number (CN) increase in these regions in invasive AdCa. CN data from an annotated Cancer Genome Atlas data set (total of 664 LADC samples) were combined with 43 AIS/MIA and 26 LPA. The RELN gene at 7q22 was selected for correlative immunohistochemistry (IHC) with its protein product reelin. IHC using Clone G10 (Novus USA) was performed on 478 LADC samples and read independently by 2 pathologists. Cytoplasmic positivity was scored for intensity (0–3) and percentage; an H-score was calculated for each (0–300).

Results: Combined CN data showed 8% to 26% gains in RELN in invasive patterns of AdCa when compared with 28% loss in AIS/MIA. Increased reelin IHC scores were seen for most LADC invasive patterns including acinar, mucinous, lepidic, and papillary subtypes (median scores 100, 100, 200, and 100, respectively) when compared to AIS/MIA (median score, 50). No association with survival was seen.

Conclusions: Reelin is a candidate biomarker of invasion in LADC. Potential diagnostic applications include the use of IHC/CN in small biopsy and cytology specimens where there is morphologic overlap among lepidic pattern lesions.

Pulmonary ossification can be idiopathic or secondary to chronic lung, cardiac, or systemic disorders. Idiopathic diffuse pulmonary ossification (IDPO) is a very rare disorder that usually occurs in men aged 40 to 60 years. It is a progressive, chronic disorder that is characterized by the presence of mature bone in alveolar or interstitial spaces, either localized or disseminated throughout the lung parenchyma. Dendriform IDPO is distinguished from the nodular form by mature bone that contains bone marrow elements. A 29-year-old man was admitted to hospital with increasing dyspnea, dependent on physical activity, for 12 months. Chest radiography showed diffuse reticular nodular infiltration in both lungs. Laboratory test results, including tuberculin skin test, white cell count, ESR, calcium, alkaline phosphatase, urea, creatinine, and liver function, were all normal. A 24-hour urine calcium excretion test result was normal. He was a medical doctor and his past medical history was unremarkable. The patient underwent left posterolateral thoracotomy and wedge resection was performed. Postoperatively, the patient had an uneventful recovery and was discharged. Grossly, sample of lung was rigid and measured 2.0 × 2.0 × 1.0 cm. Microscopic examination showed small osseous fragments in alveolar lumina and interstitium. Some bone spicules contained bone marrow elements such as hematopoietic and fat cells. There was interstitial fibrosis in some areas of lung parenchyma without septal inflammation. There was no evidence of granulomas or malignancy. It was diagnosed as consistent with dendriform pulmonary ossification. Early recognition of this disorder in young people may reduce the mortality associated with this disease process.

Context: Extraintestinal pulmonary manifestations of inflammatory bowel disease (IBD) are uncommon but protean, and include necrobiotic nodules, defined as sterile aggregates of neutrophils with necrosis, with/without epithelioid histiocytes. The etiology of necrotic pulmonary nodules in patients with IBD poses a diagnostic dilemma and includes malignancy, autoimmune disease, infection (treatment with immunosuppressives), and IBD involving the lung. Necrobiotic nodules, although rare in IBD, have been described appreciably more often in ulcerative colitis than in Crohn disease. The aim of this study was to determine the frequency and etiology of necrotic pulmonary nodules in Crohn disease.

Design: Surgical pathology reports for all lung and pleural specimens evaluated at our institution between 2000–2014 were searched for terms related to necrotic nodules/granulomas. The medical records of these patients were examined to identify those with IBD. Finally, the histopathology was reviewed in patients with IBD and necrotic pulmonary nodules.

Results: Of the 175 cases identified with necrotic pulmonary nodules, 5 were associated with Crohn disease and 1 with ulcerative colitis. In the Crohn disease cases, secondary causes such as infection were excluded, and all 5 cases met the histopathologic criteria for necrobiotic nodules. The single case of ulcerative colitis was culture positive for Mycobacterium tuberculosis.

Conclusions: Crohn disease as a primary etiology for necrotic pulmonary nodules is not as rare as presently believed, and may represent the most frequent cause in patients with Crohn disease. It is important to be aware of this to avoid delay in diagnosis and in instituting appropriate therapy.

Context: The incidence of lung cancer in Saudi Arabia is approximately 4.5% according to the Saudi Cancer Registry. The prevalence of fusion gene echinoderm microcomputer-associated protein-like 4, anaplastic lymphoma kinase (EML4-ALK) gene rearrangement in the kingdom of Saudi Arabia needs to be studied and compared with international data.

Design: This is a retrospective study, since as of July 2012 all patients confirmed to have adenocarcinoma of lung origin are tested for EML4-ALK. The test is performed by using fluorescence in situ hybridization in Clarient GE laboratories in the United States. With break-apart probes from Vysis (Abbott Molecular), a total of 128 patients were tested.

Results: Five of 128 patients (3.9%) had an EML4-ALK–positive result. All were men, with an age range of 25 to 77 years; 2 were nonsmokers, 1 was a smoker, and the smoking history for the remaining 2 was not available. The histology of 3 cases is poorly differentiated solid pattern; 2 of the 3 had mucinous component in addition. The fourth case was micropapillary and acinar, and the fifth case was mucinous. Two patients (77- and 68-years-old) were deceased. The other 3 patients are alive (25, 26, and 36 years).

Conclusions: The incidence of EML4-ALK mutation in Saudi patients in 1 center was found to be similar to published data (3%–7%). All patients who tested positive were men. The poorly differentiated histology in our patients tended to predominate. A comprehensive multicenter study is recommended with histologic and clinical correlation in the Gulf region.

Context: Grading of acute rejection in lung allograft biopsies is based on presence of perivascular and airway characteristic mixed inflammatory cell infiltrates. In acute vascular rejection (graded A2–A4) endothelialitis and endothelial cell hyperplasia are often seen. Transbronchial biopsies from the lung allograft commonly contain bronchus-associated lymphoid tissue (BALT). BALT is composed of T and B lymphocytes, and follicular dendritic cells centered on high endothelial venules (HEVs). HEVs are lined by plump endothelial cells and contain a large number of lymphocytes in their walls. Monoclonal antibody MECA-79 recognizes carbohydrate epitope on HEVs in lymphoid tissue but does not react with postcapillary venules or large vessels in nonlymphoid tissue.

Design: We reviewed 429 transbronchial biopsies from lung allografts and selected 57 cases of BALT and 13 cases of rejection and stained them with MECA-79 antibody. We evaluated vessels in BALT and vessels in rejection for the presence or absence of endothelial cytoplasmic and membranous staining.

Results: Fifty-four of 57 BALT cases (95%) stained positively for MECA-79, while all 13 cases of acute vascular rejection were negative, a significant difference (P < .001).

Conclusions: MECA-79 is reliable in distinguishing venules present in BALT from the vessels/airways involved in acute rejection and can be used in difficult cases when the distinction between BALT and rejection cannot be made on morphologic basis alone.

Context: Transbronchial biopsies using standard forceps (FTBBxs) can be limited by crush artifact and small fragment size. Cryoprobe biopsies (CPBxs) have recently become available for use in bronchoscopy. We have evaluated the safety and tissue quality of CPBx in 30 lung transplant patients undergoing surveillance biopsies and compared the results to matched FTBBxs.

Design: The biopsies were performed on 30 lung transplant patients between November 2011 and December 2013. Inclusion criteria included age >18 years and bilateral orthotopic lung transplant. Exclusion criteria were coagulopathy, FEV₁ < 0.8 L, diffuse bullous disease, hemodynamic instability, and severe hypoxemia (Pao₂ < 55 mm Hg or Spo₂ < 92% on room air). Patients were monitored for complications including pneumothorax, hemodynamic instability, and/or respiratory distress. The biopsies were quantified on digitalized slides. The pathologic findings were evaluated and recorded for both specimen types and compared.

Results: The cohort included 30 patients (11 women and 19 men; median age, 55 years). Specimen and alveolated area were greater when using CPBx than FTBBx. The diagnosis was the same except in 1 CPBx upgraded to A1BX from A0BX, while another CPBx showed a granuloma not present in the FTBBx. No clinically significant complications occurred and all patients were discharged the day of the procedure. None of the biopsies contained pleural tissue.

Conclusions: Cryoprobe biopsy is a safe, alternative technique to FTBBx during post–lung transplant bronchoscopy that can provide larger alveolated lung parenchyma. Further studies are needed to determine if larger samples obtained with CPBx translate to an increased diagnostic yield.

We present the case of a 61-year-old woman with a primary glomus tumor of the lung. Primary glomus tumors of the lung are rare and limited to a handful of case reports in the literature. Typically, these benign neoplasms, derived from glomus cells surrounding arteriovenous anastomoses, are seen in subungual regions. The woman had a history of grade II invasive ductal carcinoma of her breast with positive axillary lymph nodes; computed tomography scan was performed to look for additional metastases. She was found to have a 1.0-cm lobulated nodule in the superior segment of her right lower lung lobe that was biopsied as suspicious for metastatic breast cancer. Histopathologic examination revealed sheets of homogeneous, mid-sized cells with small round nuclei and clear to pink cytoplasm. Intratumoral thin- and thick-walled vessels were noted. Immunohistochemistry was instrumental in diagnosis, revealing strong and diffuse positivity for smooth muscle actin and vimentin. Pertinent negative staining included pancytokeratin (AE1/AE3), synaptophysin, CD56, CD34, S100, melanoma cocktail, HMB-45, calretinin, and CD45. In addition, electron microscopy demonstrated smooth muscle differentiation of the tumor cells. No necrosis or mitotic activity was observed and a diagnosis of a benign glomus tumor was made. While rare, these tumors should enter into a differential diagnosis of incidental lung nodules.

Context: Molecular alterations associated with lung adenocarcinoma (ACA) are also seen in adenosquamous carcinoma (ASqC). Currently, the diagnosis of ASqC requires both squamous cell carcinoma (SqCC) and ACA components on histologic examination with each comprising at least 10% of the tumor. However, the prevalence and significance of a minor ACA component (<10%) in otherwise classic SqCC, especially its molecular alterations, have not been well documented.

Design: Tissue microarrays were constructed by using 178 cases of primary treatment, naive lung SqCC. Immunohistochemical and histochemical staining (TTF-1, napsin A, CK5/6, p40, and mucicarmine) was performed. A multiplex polymerase chain reaction–based platform for common driver mutations and fluorescence in situ hybridization were performed to investigate molecular alterations.

Results: Ten cases (5.6%) were identified as solid ACA. Eleven cases (6.1%) with ACA components comprising less than 10% of tumor were identified. Of these 11 cases, molecular testing revealed IDH1 and PIK3CA mutations in 1 and 2 cases (9% and 18%), respectively, and FGFR amplification in 1 case (10%). KRAS mutations and FGFR amplification were found in 2 cases and 1 case of solid ACA (20% and 10%), respectively. TP53 mutations were found in 1 case each of solid ACA (10%) and SqCC with minor ACA components (9%).

Conclusions: Minor ACA components are seen in a significant minority of otherwise classic SqCCs. Based on morphology solely, solid ACA is not infrequently misinterpreted as SqCC. Given the clinical implications of the distinction, greater emphasis should be placed on identifying and reporting the presence of ACA components. The threshold for immunohistochemistry should be lowered to improve the sensitivity for detecting solid ACA.

Pulmonary fibroelastosis is a novel entity, primarily described in 2004. This diagnosis in small biopsies is challenging for pathologists. This case is that of an 86-year-old woman who clinically presented with cough and dyspnea. After clinical examination and high-resolution computed tomography (HR-CT), a cryobiopsy was obtained. The results were presented in a multidisciplinary conference. The HR-CT showed fibrotic changes with subpleural traction and bronchiectasis increasing from apical to caudal. There were consolidations on the basis of both lower lobes. Such changes are not typical for a usual interstitial pneumonia pattern. The cryobiopsy presented lung tissue with a uniform fibrotic thickening of the septa, particularly uncommon heavy elastosis, and near absence of inflammatory reaction. A diagnosis of fibrosing nonspecific interstitial pneumonia seemed unlikely. In the context of multidisciplinary discussion and considering all findings, pleuropulmonary fibroelastosis with unusual (reverse) presentation was diagnosed. We found that an interdisciplinary approach using the additional insights from cryobiopsy enabled a better verification of a difficult diagnosis in interstitial lung diseases. Clinicians should also be aware of pleuropulmonary fibroelastosis in atypical radiologic presentations with a maximum of consolidations not in the upper but in the lower lobes.

The L858R point mutation of exon 21 of EGFR accounts for up to 45% of EGFR-mutated lung adenocarcinomas (LACs). EGFR (L858R) mutation–specific antibody has been shown to have high positive predictive value (99%–100%). HER2 amplification is known to be a mechanism of acquired resistance to erlotinib. False-positive staining of EGFR (L858R) by immunohistochemistry (IHC) has been reported in ER+, HER-amplified breast carcinomas, but not in LAC. We identified 2 LACs positive for both EGFR L858R (2–3+) and HER2 (3+) by IHC. Targeted gene sequencing was performed to confirm the underlying molecular abnormality and to uncover potential cross-reactivity. Patient 1 was a 57-year-old man with stage IV LAC. Staging node biopsy showed metastatic adenocarcinoma diffusely positive for EGFR L858R by IHC. Sequencing revealed no EGFR (L858R) mutation, but amplification of HER2. HER2 was also 3+ positive by IHC. Patient 2 was a 52-year-old man with progression while taking erlotinib for LAC with EGFR exon 19 deletion. Rebiopsy of the primary tumor showed focal strong positivity for EGFR (L858R) by IHC, despite lack of EGFR (L858R) mutation by sequencing. HER2 was 3+ by IHC in the same cells that were EGFR L858R positive by IHC. We demonstrate 2 examples of false positivity for EGFR L858R by IHC. Structural homology between HER2 and EGFR might partially explain the cross-reactivity; however, further studies are needed to elucidate the frequency and mechanism of this event.

Context: The morphologic and immunohistochemical interpretation of lung allograft biopsies for antibody-mediated rejection (AMR) is not yet well defined and the diagnosis of AMR represents a diagnostic challenge for pathologists and transplant physicians alike.

Design: We investigated the cases of 78 patients who underwent lung allograft transbronchial biopsies between June and September 2013 and testing for donor-specific antibodies (DSAs) and non–donor specific antibodies (non-DSAs) by Luminex, with staining with C4d by immunohistochemistry.

Results: Acute cellular rejection (ACR) was found in 32% of patients and 19% showed other morphologic findings not associated with ACR. DSAs were present in 50% of the cases analyzed. Significant findings included class I DSA correlation with C4d in interstitial capillaries (ICs) (r = 0.31, P = .05, odds ratio [OR] = 1.79). Non-DSAs were seen in 65% of cases. They most significantly correlated with C4d in the walls of arteries and veins (OR = 5.43, P < .002) in combined class I and class II cases. Additional associations included C4d in the mucosa/submucosa (OR = 1.93) of class I and class II cases and in the walls of arteries and veins (OR = 2.22) in class I cases. Class II associations included C4d in ICs (OR =1.62), stromal/fibroconnective tissue (OR = 1.6), mucosa/submucosa (OR = 1.57), and in the walls of arteries and veins (OR = 1.35).

Conclusions: Our findings suggest that C4d staining of interstitial capillaries is correlated with DSAs and non-DSAs in the recipient and that both types of antibodies may influence humoral immunity in lung allografts.

Context: Pulmonary manifestations of immunoglobulin G4–related disease (IgG4-RD) are diverse, but nodular lymphoid hyperplasia (NLH) is not a well-documented manifestation. Recently, Epstein-Barr virus (EBV) was found in IgG4-related lymphadenopathy. We postulated that a subset of NLH cases might represent IgG4-RD with EBV-positive lymphocytes as in IgG4-related lymphadenopathy.

Design: Immunohistochemistry with IgG and IgG4 was performed on 26 NLH cases in our files (1994–2014) and on 9 controls including diffuse lymphoid hyperplasia without nodule formation (n = 2), usual interstitial pneumonia with increased lymphoplasmacytic infiltrates (n = 5), and reactive mediastinal lymph nodes (n = 2). IgG4+ and IgG+ cells were counted from 3 high-power fields (HPF) in hot spots. EBV in situ hybridization (ISH) was performed in cases with high IgG4+ count (n = 15).

Results: Average IgG4+ plasma cell count in NLH was 43 per HPF (range, 2–139) with average IgG4+ to IgG+ ratio of 0.25 (range, 0.03–0.46). Three of 26 cases had a markedly increased IgG4+ count (range, 55–139) and IgG4+ to IgG+ ratio (>0.4). No serum IgG4 level was available in these cases. The average IgG4+ count of control cases was 36 per HPF (range, 0–92) with average IgG4+ to IgG+ ratio of 0.34 (range, 0.0–0.67). EBV-ISH was negative in all cases tested.

Conclusions: The average IgG4+ count and IgG4+ to IgG+ ratio in our 26 NLH cases were below the thresholds for pulmonary IgG4-RD and lacked significant difference from non-NLH cases. However, 3 of 26 NLH cases met the criteria for IgG4+ cells recommended by the consensus guideline, suggesting a possibility that a subset of NLH cases might be associated with IgG4-RD. EBV does not seem to play a role in this cohort.