A 57-year-old man presented to his primary care physician with a solid dermal mass in the volar aspect of his left ring finger between the metatarsophalangeal and distal interphalangeal joints. The lesion had been present for an unknown period. It had recently enlarged to approximately 2.0 cm. His medical history was significant for atherosclerosis, with stenosis of the left carotid artery. The patient was referred to a surgeon, and an excisional biopsy was subsequently performed.
Grossly, the specimen consisted of a soft tan-white 1.4 × 1.3 × 1.3-cm dermal tumor nodule beneath unremarkable skin. The entire tumor was processed routinely and submitted for microscopic evaluation. At low magnification, sections showed an unremarkable epidermis of digital skin. In the dermis, there was a tumor nodule composed of solid and cystic areas (Figure 1). In general, the lesion was well circumscribed, but foci of peripheral infiltration into the surrounding stroma were also present (Figure 2). The solid areas consisted of back-to-back fused glands that often contained eosinophilic secretory material or necrotic debris (Figure 3). The glands were lined by 2- to 3-layer cuboidal to columnar cells showing moderate cytologic atypia, with occasional small nucleoli. In cystic areas, micropapilla without distinct fibrovascular cores were focally identifiable (Figure 4). The overall mitotic count was in the range of 3 to 4 per 10 high-power fields. The dermal tumor was separated from the overlying epidermis by a distinct grenz zone (Figure 1). There was no bone, cartilage, or subcutaneous adipose tissue present in the specimen. The lesion extended close to the deep margin of the excision. Immunostaining was not performed.
What is your diagnosis?
Pathologic Diagnosis: Aggressive Digital Papillary Adenocarcinoma
Abstract
A 57-year-old man presented with a solid dermal mass in his left ring finger. Excisional biopsy demonstrated a solid cystic dermal lesion of approximately 1.4 cm in greatest dimension. Microscopic analysis showed a well-circumscribed cystic neoplasm. Back-to-back fused glands and foci of micropapilla occupied the solid areas within the lesion. Neoplastic cells showed moderate cytologic atypia with low mitotic count. The clinical presentation and morphologic attributes were characteristic of aggressive digital papillary adenocarcinoma, a rare malignant skin adnexal neoplasm. The favored approach is complete excision of the primary tumor, with sentinel lymph node biopsy, as no morphologic features differentiate it from its putative benign counterpart. Because this tumor is rare, it is important to be aware of its existence and to include it in the differential diagnosis of solid cystic lesions in the dermis or soft tissue of the finger.
Aggressive digital papillary adenoma/adenocarcinoma (ADPA/ADPAca) was first described by Helwig1 in 1984. It is a rare eccrine gland neoplasm that occurs most commonly in the digital skin of men in their fifth to seventh decades of life. The entity typically presents as a subcutaneous soft tissue mass or cyst in the distal volar aspect of the fingers. Initial clinical impressions of this lesion include ganglion cyst, foreign body granuloma, pyogenic granuloma, epidermoid cyst, squamous cell carcinoma, hemangioma, giant cell tumor, osteomyelitis, and an infectious process.2,3 In their 1987 clinical pathologic study, Kao et al4 distinguished ADPAca from ADPA, based on poor glandular formation, necrosis, cellular atypia, nuclear pleomorphism, invasion of soft tissue and bone, and vascular permeation. They attributed distant metastasis and fatality of ADPAca to the presence of these histologic findings. In a recent retrospective series, however, Duke et al2 studied 67 cases (originally diagnosed as ADPA and ADPAca) and found that none of those clinical and histologic findings reliably predicted the biologic behavior of this unusual tumor. Therefore, they concluded that all aggressive digital papillary neoplasms should be designated as ADPAca.
Characteristically, ADPAca is a cystic or nodular dermal neoplasm that can have a well-circumscribed or infiltrative border. When epidermis is included in the initial biopsy specimen, a grenz zone is often present, separating the tumor from the overlying epidermis. In the solid areas, one finds back-to-back fused glands, lined by cuboidal or low columnar cells. The cysts are formed by central degeneration or necrosis of the tumor. Another frequent finding is papillary projections into these cystic spaces. These papillae may or may not contain fibrovascular cores. Focal squamous metaplasia, clear cell changes, stromal hyalinization, decapitation secretion, and myxoid changes can also be seen.2 When examined under high magnification, the tumor cells demonstrate mild to moderate cytologic atypia, while frank anaplasia is not observed. The mitotic index ranges from 0 to 60 per high-power field.2 Immunostaining is not required, as the clinical and histologic features are characteristic of this lesion. However, when studied, the tumor cells expressed cytokeratins, carcinoembryonic and S100 antigens, and ferritin, consistent with eccrine histogenesis.2,5 Aggressive digital papillary adenocarcinoma can behave in an invasive fashion. Local recurrence and nodal and pulmonary metastases are well documented.2,6–8 The literature advocates complete excision or amputation of the affected digit, with sentinel lymph node biopsy.9,10 Duke et al2 showed that only 5% of the tumors recurred when treated by reexcision following initial biopsy, while 50% recurred when not so treated. In addition, 14% of their patients developed metastasis, and 3 of them died of the disease. These data underscore the importance of definitive therapy with reexcision or amputation following the initial diagnosis. Since its first description by Helwig,1 few studies of the disease have been published in the literature.2,4 It remains a rare entity, and general pathologists may not be aware of the lesion. It is important to include this entity in the differential diagnosis when one is confronted with a mass or cystic lesion from digital skin.
Our patient underwent amputation of the affected finger, with ipsilateral axillary sentinel node biopsy. No residual or metastatic carcinoma was found in the primary site or the lymph node. In addition, chest computed tomographic scan and recent clinical follow-up identified no metastatic lesions.
References
The authors have no relevant financial interest in the products or companies described in this article.