According to the Bismuth-Corlette classification system, perihilar cholangiocarcinomas extending into the right secondary intrahepatic ducts are classified as

Perihilar cholangiocarcinomas, also referred to as Klatskin tumors, are fuher classified based on anatomic location by the Bismuth-Corlette classification. Type I tumors are confined to the common hepatic duct, but type II tumors involve the bifurcation without involvement of the secondary intrahepatic ducts. Type IIIa and IIIb tumors extend into the right and left secondary intrahepatic ducts, respectively. Type IV tumors involve both the right and left secondary intrahepatic ducts.