Intraductal papillary neoplasm of the bile duct, gastric type, arising in the intrapancreatic common bile duct could progress to colloid carcinoma: report of a case

Intraductal papillary neoplasm of the bile duct (IPNB) exists in a pathway of multistep-carcinogenesis toward cholangiocarcinoma. Four subtypes are observed in IPNB, pancreatobiliary type, intestinal type, gastric type, and oncocytic type, similarly to the corresponding disease in the pancreas, intraductal papillary mucinous neoplasm (IPMN). IPNB can present with or without macroscopically visible mucin secretion. IPNB usually progresses to tubular adenocarcinoma. However, there are a limited number of well-described cases of gastric-type IPNB progressing not to tubular adenocarcinoma but to colloid carcinoma. Herein, we present a case of an 82-year-old female patient with gastric-type IPNB in the intrapancreatic common bile duct without macroscopically visible mucin secretion, which progressed to colloid carcinoma. As IPNB, especially without visible mucin secretion, is considered to be a heterogeneous group of diseases, such an unexpected association could occur.