Intracholecystic papillary neoplasm arising in a patient with pancreaticobiliary maljunction: a case report

BACKGROUND: Pancreaticobiliary maljunction (PBM) is a congenital abnormality in which the pancreatic and biliary ducts join anatomically outside the duodenal wall resulting in the regurgitation of pancreatic juice into the biliary tract (pancreatobiliary reflux). Persistent pancreatobiliary reflux causes injury to the epithelium of the biliary tract and promotes the risk of biliary cancer. Intracholecyctic papillary neoplasm (ICPN) has been highlighted in the context of a cholecystic counterpart of intraductal papillary mucinous neoplasm of the pancreas and the bile duct, but the tumorigenesis of ICPNs remains unclear. CASE PRESENTATION: A 52-year-old Japanese woman was referred for the assessment of dilation of the bile duct. Computed tomography which revealed an enhanced mass in the gallbladder and endoscopic retrograde cholangiopancreatography confirmed that the confluence of the main pancreatic duct and extrahepatic bile duct (EHBD) was located outside the duodenal wall. Under the diagnosis of gallbladder cancer with PBM, cholecystectomy with full thickness dissection, EHBD resection, lymph node dissection, and hepaticojejunostomy were performed. Macroscopic examination of the resected specimen showed that the cystic duct was dilated and joined into the EHBD just above its confluence with the pancreatic duct, and the inflamed change of non-tumorous mucosa of gallbladder indicating that there was considerable mucosal injury due to pancreatobiliary reflux to the gallbladder. Histopathological examination revealed that the gallbladder tumor was a gastric-type ICPN with non-invasive component. Either KRAS gene mutation or p53 protein expression that were known to be associated with the carcinogenesis of biliary cancer under the condition of pancreatobiliary reflux was not detected in the tumor cells of ICPN. CONCLUSION: The present case might suggest that there was no association between PBM and ICPN. To reveal the tumorigenesis of ICPN and its attribution to pancreatobiliary reflux, however, further study is warranted.