The cytologic and immunohistochemical findings of pancreatic mixed acinar-endocrine carcinoma

Abstract

Background: The classification of epithelioid pancreatic neoplasms based on fine-needle aspiration (FNA) is important for proper management, as distinction of pancreatic neuroendocrine neoplasms from other similar appearing lesions can result in significantly different treatment. Mixed acinar-endocrine carcinomas (MAEC) are genetically related to acinar carcinomas and are treated as such. We reviewed cases of MAEC to better characterize their cytologic and immunohistochemical features.

Methods: Eight FNAs of MAECs were identified and reviewed. A chart review for each case was conducted.

Results: All patients were male, 42-68 years of age, and presented with either Stage 3 or 4 disease. Smear backgrounds of all cases showed naked nuclei without significant necrosis. The smears were cellular with cells arranged in either three-dimensional (3D) clusters with intervening capillaries or singly dispersed. Acinar formation was a prominent feature. Cells were round to oval with small to moderate amounts of delicate cytoplasm. The nuclei were round to oval with mild to moderate anisonucleosis with granular chromatin and small nucleoli. Apoptotic bodies and mitoses were noted in most cases, with Ki67 indices of 10%-48%. All tumors, by definition, demonstrated expression of trypsin and synaptophysin with variable chromogranin expression (50%).

Conclusion: The cytology of acinar cell carcinoma shares features with aspirates of other nonductal adenocarcinoma neoplasms of the pancreas. A clue to the diagnosis is that tumors show high Ki67 indices and a diagnosis of MAEC should be excluded anytime a diagnosis of Grade 2 or 3 well-differentiated neuroendocrine tumor or high-grade neuroendocrine carcinoma is in the differential.