A 32-year-old white woman was admitted to our hospital for investigation of severe microcytic anemia. Initial findings included a hemoglobin level of 59 g/L; hematocrit, 0.20; leukocyte count, 1.3 × 109/L; and platelet count, 309 × 109/L. Personal history was unremarkable except for essential hypertension and obesity.
A large mass situated in the right flank was found on physical examination. Radiography and endoscopic examination suggested an ulcerated tumor of the upper duodenum. The lesion produced partial intestinal obstruction and displaced adjacent structures. Further studies pointed to the mass being consistent with an ulcerated duodenal leiomyoma, although at this time a biopsy could not be taken due to the risk of hemorrhage. The patient started suffering from abdominal pain and dyspepsia. Removal of the tumor was recommended.
Preoperative studies, which included computed tomography and abdominal ultrasonography, demonstrated an 11 × 8.5-cm abdominal mass, supporting the first diagnosis of duodenal leiomyoma. Preoperative biopsy of the duodenum revealed inflammatory elements with no malignancy in the samples retrieved.
Surgical exploration revealed a mass located in the retroperitoneum, between the head of the pancreas and the duodenum, infiltrating the superior mesenteric vein and thus precluding local resection. The surgeons believed that the tumor originated in the pancreas rather than the duodenum, although they could not be sure of the origin owing to the size of the mass and because it affected several structures. Surgery was especially complicated owing to venous invasion and the large size of the mass. A gastrojejunostomy was performed, and 4 units of blood were required. There was no involvement of the liver, spleen, or lymph nodes.
Five days after the first operation, the patient suffered postoperative complications. On this occasion, surgical reexploration revealed suture dehiscence and fecal peritonitis. The patient developed septic shock and acute renal failure, and she died 4 days later.
Our laboratory received an irregular specimen, measuring 4 × 3 × 0.8 cm, and a few small fragments from the mass, measuring 1.5 × 1 × 0.5 cm overall. The surface of the specimen showed hemorrhagic necrosis, and it was surrounded by a well-formed fibrous capsule. The tumor was predominantly solid, showing some areas with a cystic degenerative pattern.
On microscopic examination, the compact areas showed uniform small tumor cells, which in the papillary fields surrounded thin stalks of stroma enclosing delicate blood vessels, appearing as pseudopapillae (Figure 1). Tumor cells contained round or oval nuclei with prominent nucleoli, showing a moderate amount of eosinophilic cytoplasm containing focally dense periodic acid-Schiff–positive granules (Figure 2). Distinctive features were foamy histiocytes and cholesterol clefts. Necrosis of tumor cells was common, while mitosis or atypia were absent.
The neoplastic cells expressed neuron-specific enolase, α1-antitrypsin, α1-antichymotrysin, and vimentin, while reactivity for synaptophysin was slightly positive. Reaction was negative for chromogranin, insulin, glucagon, and S100, whereas it was positive for keratin 5-D3. Reactivity for progesterone receptors was positive (Figure 3). Carcinoembryonic antigen reactivity was focally positive, although the neoplasm was free from other usual pancreatic markers.
What is your diagnosis?
Pathologic Diagnosis: Solid-Pseudopapillary Tumor of the Pancreas
Solid-pseudopapillary tumor (SPT) is an unusual low-grade malignant neoplasm of the pancreas that occurs more frequently in young women. Since Frantz1 described the first case in 1959, more than 300 other cases have been reported, with 2 references to extrapancreatic locations.2,3 We report the features of a case of SPT situated in the retroperitoneum adjacent to the pancreas, initially misdiagnosed by several imaging methods.
Patients with SPT usually present with symptoms relating to compression, such as vomiting, abdominal discomfort, or fullness. Most often physical examination reveals a palpable mass.
Spread is usually limited to local invasion, and in the rare cases of metastases, the clinical course is much better than for other pancreatic neoplasms. Few cases of metastases have been reported, all of which were to the liver. Only Cappellari et al4 described a patient with widespread intra-abdominal metastases; this patient experienced subjective improvement and was alive without disease 15 months after palliative resection.
Morphologic and immunochemical features characterize these neoplasms, as well as the preponderance of young female patients.
The gross appearance is that of a mass with an average diameter of 10.5 cm; a fibrous pseudocapsule usually surrounds the tumor. Solid-pseudopapillary tumor may appear in any portion of the pancreas, although it is more frequent in the tail. Cystic areas and large hemorrhagic necrotic areas are caused by damage to the delicate vascular network that traverses this tumor.
Microscopically, the tumor cells have round or oval nuclei with prominent nucleoli that exhibit an eosinophilic, clear, or vacuolated, moderately abundant cytoplasm. Characteristically, intracellular and rarely extracellular periodic acid-Schiff–positive hyaline globules may be present.
The histologic appearance depends on the location within the neoplasm. Solid areas show sheets of uniform, polygonal, epithelioid cells separated by delicate blood vessels. Perivasal stroma may show sclerosis in the central parts, which reduces the permeability of capillaries and leads to necrosis5; these degenerative changes are the cause of the cystic spaces and the hemorrhagic areas.
Pseudopapillae result when several layers of tumor cells with nuclei oriented away from the capillary surround a central vessel. Mitoses are extraordinarily rare, and nuclear atypia is very uncommon as well.
The neoplastic cells express vimentin, α1-antitrypsin, α1-antichymotrysin, neuron-specific enolase, and very often progesterone receptors, whereas estrogen receptors usually have been described as absent. They are focally positive for keratin, and 10% to 15% of cases are positive for synaptophysin, while immunohistochemical staining for chromogranin, insulin, and glucagon is negative.
The differential diagnosis should include nonhyperfunctioning islet cell tumors, acinar cell carcinomas, mucinous cystic neoplasms, microcystic adenomas, and pancreaticoblastoma.6
Many studies have attempted to identify a cell of origin for SPT, with some studies suggesting that the tumor originates from pluripotential embryonic stem cells. However, none of the data have clarified the nature of this tumor. Solid-pseudopapillary tumor is currently accepted as a neoplasm without a definable corresponding normal cell type.7
In conclusion, SPT is a low-grade malignant neoplasm of the pancreas that shows a predilection for young females and has an excellent prognosis with complete surgical resection, in spite of metastases. As such, we believe it is very important to suspect this tumor, especially among young women presenting with an upper abdominal mass of uncertain origin.
References
Reprints not available from the authors.
