Figure 1.

According to the relative anatomical location with the liver, CCA is divided into three types: ICC, pCCA and dCCA. ICC is defined as bile duct cancer located inside the liver, and the histological types are classified as mass-forming, periductal infiltrating, and intraductal growing. pCCA is defined as a secondary branch located in the hepatic duct (from the common bile duct above the cystic duct to the liver) and histologically as a Klatskin tumor. dCCA refers to distal cholangiocarcinoma located extrahepatically, and the histological type is mainly adenocarcinoma.