Hilar cholangiocarcinoma: Pathology and tumor biology

Hilar cholangiocarcinoma,first described by Klatskin in 1965,is a relatively rare tumor arising from the bile ducts.The histomorphological features of hilar cholangiocarcinoma are identical with other extra-and intra-hepatic bile duct carcinomas.The most common disease associated with cholangiocarcinoma is primary sclerosing cholangitis.The development of cholangiocar-cinoma is a multistep process associated with several mutations in oncogenes and tumor-suppressor genes.Based on macroscopic appearance,three distinct subtypes have been described:sclerosing,nodular,and papillary.Microscopically,more than 95%of tumors are adenocar-cinomas.Hilar cholangiocarcinoma is a slowly growing tumor and tends to spread longitudinally along the bile ducts with neural,perineural,and subepithelial extension.Lymph node invasion can be found in 30%–50%patients at the time of diagnosis,but blood-born metastases are rare and usually occur at late stages.