Extrapancreatic Solid Pseudopapillary Neoplasm in the Subhepatic Region: A Diagnostic Dilemma

Abstract

Solid pseudopapillary neoplasm (SPN) is a rare but distinctive pancreatic neoplasm that typically affects young women. Rare cases of extrapancreatic SPN have been reported. Here; we present an unusual case of SPN in a 32- year-old woman who presented with vague abdominal pain. Computed tomography scan revealed a large solid mass in the subhepatic region; adjacent to the head of pancreas and second part of duodenum. The pancreatic gland parenchyma was not involved. Radiologic features were suggestive of a gastrointestinal stromal tumor. On microscopic examination, the lesion exhibited both solid and pseudopapillary pattern with prominent myxoid change in the stroma. Immunohistochemistry showed strong expression of vimentin, CD10, CD56 and alpha 1 antitrypsin. Synaptophysin was focally positive. β-catenin immunostain showed strong nuclear expression; while stain for Ecadherin was negative. Stains for cytokeratin;epithelial membrane antigen; chromogranin A; calretinin; carcinoembryonic antigen and S-100 protein were negative. These morphologic and immunohistochemical features were characteristic of SPN. We present this case to highlight the importance of recognizing SPN at an unusual location. Differentiation from neuroendocrine tumor can be particularly challenging due to their overlapping clinical; radiologic; morphologic and immunohistochemical features.