Pancreatic mixed acinar-neuroendocrine carcinoma, a unique diagnostic challenge on FNA cytology: A small series of two cases with literature review.

Mixed acinar-neuroendocrine carcinoma (MANEC) of the pancreas is a rare tumor. We present two cases of MANEC diagnosed on endoscopic ultrasound (EUS) guided fine-needle aspiration (FNA). The first patient is a 33-year-old male who had a 3.6 cm mass in the uncinate process and liver metastasis. The second patient is a 66-year-old male with a 10 cm mass in the pancreatic tail. The FNA smears from both cases were hypercellular with neoplastic cells in loosely cohesive clusters and many naked nuclei. In both cases, the tumor cells were positive for CKAE1/3, synaptophysin, chromogranin, and trypsin by immunohistochemistry. Final diagnoses of MANEC were rendered based on cytological features and immunohistochemical profiles. To date, 44 cases of MANEC have been reported in the English literature, only three of which were diagnosed on cytopathology specimens before surgical resection. Our report adds two more cases diagnosed on cytopathology alone. Herein, we discuss the various cytomorphologic and clinical features of MANEC and present a brief review of the literature. Diagn. Cytopathol.