Cystic endocrine tumor of the pancreas with an atypical multilocular appearance.

A 46-year-old woman with epigastric pain was found to have a cystic tumor in the pancreas head on radiological examinations. The tumor was hypervascular, and its multilocular appearance resembled the "honeycomb" pattern of serous cystic tumor (SCT). The patient underwent surgery. The cut surface of the tumor showed a thick fibrous capsule with multiple cystic components, which contained necrotic tissue and brownish serous fluid, indicating an episode of hemorrhage. The cut surface of the tumor resembled solid-pseudopapillary tumor (SPT) on gross appearance. On immunohistochemical staining, the tumor cells showed diffuse and strong staining for synaptophysin (SYN), chromogranin A (CGA), and grimelius, and no staining for alpha 1-antitrypsin or CD10. We finally made a diagnosis of pancreatic endocrine tumor (PET). As PET sometimes shows an atypical multicystic appearance, immunohistochemical staining is mandatory for its correct diagnosis.