Pancreatic Neuroendocrine Neoplasm Concomitant with Branch-duct Intraductal Papillary Mucinous Neoplasm: A Case Report and Literature Review.

Reports of pancreatic neuroendocrine neoplasm (P-NEN) concomitant with intraductal papillary mucinous neoplasm (IPMN) are gradually increasing. However, many of these cases were diagnosed in the resected specimen incidentally. We herein report a case of minimal P-NEN concomitant with branch-duct IPMN that was successfully diagnosed preoperatively by contrast-enhanced endoscopic ultrasonography (EUS) and an EUS-guided fine-needle biopsy. These findings suggest that P-NEN as well as pancreatic ductal adenocarcinoma should be considered as concurrent tumors developing in patients with IPMNs. EUS is an essential modality when evaluating IPMN for detecting small lesions concomitant with IPMN.