Solid Pseudopapillary Tumor of the Pancreas Without a Cystic Component

A 38-year-old woman was referred to our hospital for further evaluation of a pancreatic mass that was noted on screening ultrasonography at another hospital. She had no complaints or any history of pancreatic disorders. Laboratory data showed no abnormalities. On computed tomography, a 20-mm-sized, well-demarcated hypoenhancing mass was seen in the body of the pancreas (Figure A; 1, precontrast phase; 2, pancreatic parenchymal phase; 3, portal venous phase). On magnetic resonance imaging, the lesion had low signal intensity on the T1-weighted image and high signal intensity on the T2-weighted image (Figure B). On both computed tomography and magnetic resonance imaging, the mass had neither internal hemorrhage nor a cystic component, and there was no evidence of metastasis to lymph nodes or other organs. On magnetic resonance cholangiopancreatography, there were no abnormal findings in the main pancreatic duct. On endoscopic ultrasonography, the mass was well-defined, nonhomogeneous, and hypoechoic. Preoperatively, an atypical, nonfunctioning endocrine tumor or an atypical, solid pseudopapillary tumor (SPT) of the pancreas was suspected. We performed a distal pancreatectomy combined with splenectomy.

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Operative findings included a large, well-defined mass located in the pancreatic body without distant metastases or involvement of adjacent organs. Macroscopic examination revealed a solid, yellow mass without cystic or hemorrhagic components. The mass was 25 × 20 × 15 mm in size, and the fibrous capsule of the tumor was present only behind the mass (Figure C). Histologically, the tumor tissue was composed of dyscohesive tumor cells with uniform, small, round to oval, centrally located nuclei and eosinophilic or clear vacuolar cytoplasm. They showed a solid monomorphous pattern with a thick fibrovascular network (Figure D), and a pseudopapillary pattern was found in very focal areas. Variable zone of hyalinization and myxomatous change was detected in some areas. No mitotic activity or tumor vascular invasion was found. The cut end of the residual pancreas was free of tumor cells. The tumor cells were immunoreactive for rather specific markers to SPT such as anti–β-catenin, CD10, cyclin D1, and progesterone receptor antibodies, but no immunoreactivity for pancreatic enzymes and pancreaticogut hormones were detected. On the basis of the histologic and immunohistochemical findings, the tumor was diagnosed as SPT of the pancreas without a cystic component. The patient's postoperative course was uneventful, and the patient was alive and disease-free at 4-month follow-up.

SPT occurs predominantly in young female patients.1 It usually presents as a large mass containing a cystic component induced by internal hemorrhage and partial necrosis.2 However, in this case, the tumor was composed of a unitary solid component. Although the pathophysiologic mechanism is unclear, no cystic component might have developed because this tumor was small. As a result of recent developments in diagnostic imaging, small SPTs can be detected. SPT should be considered in the differential diagnosis of a small, solid, well-demarcated mass without enhancement.