Anatomy and pathology of intra- and extrahepatic bile duct tumors

Adenocarcinomas of the intra- and extrahepatic bile ducts are rare tumors t hat begin with malignant transformation of the bile duct epithelia. Intrahe patic cholangiocarcinomas derive from the small bile ducts located proximal ly to the right and left hepatic ducts. Extrahepatic bile duct carcinomas o riginate in the right or left hepatic duct, the cystic duct, or the choledo chal duct. Tumors located at the bifurcation are called Klatskin tumors. Th e intrahepatic cholangiocarcinomas a re classified according to the TNM cla ssification of liver tumors, while the extrahepatic bile duct tumors have t heir own TNM classification. Several factors, accompanied by a chronic infl ammatory reaction, have been discussed in the etiopathogenesis of these tum ors: schistosomiasis, ulcerative colitis with primary sclerosing cholangiti s, and inborn bile duct cysts of the liver as a consequence of a disturbanc e of the ductal plate formation. Over 95% of bile duct tumors are adenocarc inomas. In the nomenclature of precursor lesions a two-grade classification of dysplasia (low-grade versus high-grade) has been found to be more repro ducible.