A Case of High-Grade Panin (Carcinoma In Situ) Concomitant with Intraductal Papillary Mucinous Neoplasm of the Pancreas: Can A Focal Fatty Change Hint at Peripheral Panin?

Context Intraductal papillary mucinous neoplasms of the pancreas can be associated with ordinary ductal adenocarcinomas as well as pancreatic intraepithelial neoplasias in the background pancreas; however, preoperative identification of peripheral pancreatic intraepithelial neoplasias is extremely difficult. Case report The patient was a 79-year-old male with a chief complaint of right hypochondria pain. Several imaging tests revealed a multilocular cystic lesion (6 cm in size) in the pancreatic head with communication to a mildly dilated main pancreatic duct (5 mm in diameter). Dual-echo T1-weighted imaging (T1WI) revealed subtle, focal signals suggesting fat in the upper pancreatic head. The carcinoembryonic antigen level in the pancreatic juice was elevated (1350 ng/mL), however, no malignant cells were detected by cytological examinations. Blood tumor markers were within normal ranges. Under a diagnosis of branch duct type or mixed-type IPMN, pancreaticoduodenectomy was performed. The multilocular cystic lesion was localized to the uncinate process of the pancreas, included excess mucous production, and was histologically diagnosed as non-invasive, branch duct type, intestinal-type IPMN. Conversely, apart from IPMN, small foci of high-grade PanIN corresponding to carcinoma in situ (less than 5 mm in diameter) of the peripheral pancreatic ducts were incidentally noticed within the fatty tissue, which was visualized by dual-echo T1WI. High-grade PanIN/ CIS involved periductal fibrosis and demonstrated the pancreatobiliary phenotype. Genetically, different KRAS mutants were detected in IPMN (G12R) and high-grade PanIN/CIS (G12V), respectively, and a GNAS mutation was detected in IPMN, but not in high-grade PanIN/ CIS. Conclusion A resected case of peripheral high-grade PanIN/CIS concomitant with branch duct type IPMN of the pancreas head was reported. Although this may simply be an incidental association and it is extremely difficult to preoperatively identify microscopic lesions of the peripheral ducts, secondary findings such as focal fatty change may shed light on the detection of such lesions. Received January 24th, 2016 Accepted March 11th, 2016