Spread of hilar cholangiocarcinomas via peribiliary gland network: a hither-to-unrecognized route of periductal infiltration.

Cholangiocarcinomas (CCs) show intraluminal spread to bile ducts and periductal infiltration associated with vascular, lymphatic and perineural invasion in addition to direct penetration. Recently, the peribiliary gland networks located around the hilar and extrahepatic bile ducts have been reportedly to be involved in a variety of biliary diseases. However, the pathological features and roles of these networks in the carcinogenesis and progression of CCs remain to be explored. Recently, we experienced two cases of hilar CC showing a nodular sclerosing growth grossly and histologically well-differentiated adenocarcinomas, with an extensive involvement of the peribiliary gland networks. In situ like spread of carcinoma cells in the bile duct lumen was focal in one case and not identifiable in the other. In contrast, other 4 cases of ordinary hilar CC which were also well-differentiated adenocarcinomas, showed variable intraductal luminal spread and also extensive periductal infiltration irrespective of the peribiliary gland network. In conclusion, the present study showed a unique form of periductal spread of CCs with preferential and extensive involvement of the peribiliary gland networks.