Abstract: | BCL10 was recently demonstrated to be a biomarker for pancreatic acinar cell carcinoma, but whether altered BCL10 expression can be detected in cell block specimens is unclear. Here, we report a pancreatic acinar cell carcinoma with cytological findings that showed BCL10 expression in a cell block. A 72‐year‐old man presented with a pancreatic tumor and underwent endoscopic ultrasound‐fine needle aspiration (EUS‐FNA) with additional passes performed for cell block preparation. The EUS‐FNA cytology showed loose cohesive clusters with focal acinar‐ or gland‐like‐structures and prominent nucleoli. The preoperative diagnosis was well differentiated adenocarcinoma, and he underwent a pancreaticoduodenectomy. Histological examination revealed an acinar tumor structure with tumor cells staining positive for BCL10 and trypsin. The cell block specimen also demonstrated strong and diffuse BCL10‐positive staining. Based on these findings, this tumor was diagnosed as acinar cell carcinoma of the pancreas. This case demonstrates that BCL10 expression within cell blocks facilitates a differential diagnosis of acinar cell carcinoma. Diagn. Cytopathol. 2017;45:247–251. © 2016 Wiley Periodicals, Inc. |