Pancreatic oncocytic endocrine tumors. Cytologic features of two cases

Oncocytoma designates a usually benign tumor consisting of oncocytes (cells rich in mitochondria). Rarely do endocrine pancreatic tumors show oncocytic transformation, and consequently their liver metastases may resemble a hepatocellular carcinoma.

Case 1, a 36-year-old male, presented with an 8-cm pancreatic mass with multiple liver metastases. Fine needle aspiration (FNA) biopsy was performed on the liver. The cytologic features were highly cellular material; numerous isolated cells and irregular, loose cellular aggregates; rare mitoses; round or polygonal cell shape; rosette formation; and large, granular, eosinophilic cytoplasm (suggestive of poorly differentiated hepatocellular carcinoma). Case 2, a 57-year-old female with hypoglycemia, had a 13-cm pancreatic mass. FNA material showed the same cytologic features as case 1. In situ hybridization to detect albumin mRNA was negative in both cases, while immunocytologic reactions for glandular epithelial cytokeratin and chromogranin A were positive. Case 2 was also positive for insulin.

Oncocytic transformation in endocrine tumors of the pancreas is a rare occurrence and must be kept in mind in the diagnostic workup of FNA material from tumors of the hepatopancreatic region.