Endoscopic ultrasound-guided fine-needle aspiration cytology findings from a case of ectopic pancreas of the stomach – cytological differential diagnosis with acinar cell carcinoma

Abstract

Ectopic pancreas is a relatively common lesion as gastric submucosal tumor (SMT), but it makes little mention of cytological findings in endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). Herein, we present a case of ectopic pancreas diagnosed by EUS-FNA, and discuss the cytological differential diagnosis from ACC. A 41-year-old woman was admitted to our hospital with gastric SMT, measuring 19 mm in diameter. EUS-FNA was performed. Cytologic specimens showed clustered or scattered small cells. Nuclei were relatively small and slightly irregular shaped. Their chromatin pattern was fine granular, and nucleoli were small but conspicuous. Most cells had pink granular substance on Pap staining. Histologic specimens were prepared from tiny pieces simultaneously obtained at EUS-FNA, which revealed benign pancreatic tissue with small nucleoli and eosinophilic granules. Immunohistology showed positivity for chymotrypsin. The lesion was diagnosed as ectopic pancreas. Ectopic pancreas has been reported to show slightly nuclear atypia and small nucleoli in EUS-FNA. In this case, benign acinar cells also showed slightly nuclear atypia. The findings indicate some similarities with ACC. However, ACC usually shows high cellularity compared with ectopic pancreas. It also lacks pink granular substance on Pap staining. These findings are useful to differentiate from ACC.