Cholangiocarcinoma can affect any area of the bile ducts, either within or outside the liver. Tumors occurring in the bile ducts within the liver are referred to as "intrahepatic", those occurring in the ducts outside the liver are "extrahepatic", and tumors occurring at the site where the bile ducts exit the liver may be referred to as "perihilar". A cholangiocarcinoma occurring at the junction where the left and right hepatic ducts meet to form the common hepatic duct may be referred to eponymously as a Klatskin tumor.