A wolf in sheep's clothing: a non-functioning islet cell tumor of the pancreas masquerading as a microcystic (serous cystic) adenoma.

CONTEXT: The endosonographic appearance of a microcystic "honeycomb" lesion of the pancreas usually indicates a serous cystic adenoma. CASE REPORT: We report a case of a non-functioning islet cell tumor that has the typical microcystic "honeycomb" appearance of a serous cystic adenoma. The implications for endoscopic ultrasound diagnosis and management of cystic pancreatic lesions are discussed. CONCLUSION: Islet cell tumors are a rare differential diagnosis of microcystic pancreatic lesions. If fine needle aspiration remains non-diagnostic preoperative distinction from serous cystic adenomas may be impossible.