s S73 Results: Out of 3832 EUS-FNA, we identified three cases (0.1%) that were diagnosed as acinar cell carcinoma. On cytology, only one was considered possible acinar cell carcinoma. Of the two other cases, one was diagnosed as adenocarcinoma and the other as neoplasm present, with a differential that did not include acinar cell carcinoma. On histology, two cases were diagnosed as acinar cell carcinoma, and the third was diagnosed as ductal adenocarcinoma with acinar differentiation. The PAS stain and IHC studies for trypsin and chymotrypsin show positive staining. Electron microscopy shows cytoplasmic dense zymogen granules, and one case shows elongated filamentous structures that have been reported in association with acinar cell carcinoma. Conclusions: On fine needle aspiration cytology, the differential diagnosis of acinar cell carcinoma of the pancreas includes pancreatic endocrine neoplasm, ductal carcinoma, and solid pseudopapillary neoplasm of the pancreas. In order to differentiate between these neoplasms, one must incorporate the use of ancillary techniques such as IHC. Positive staining for trypsin, chymotrypsin and PAS, along with electron microscopy, are useful markers to indicate the presence of acinar cell differentiation.