Pathology and molecular pathology of cholangiocarcinoma

Biliary tract cancers are a wide group of heterogeneous neoplasms of the biliary tree, composed of intrahepatic cholangiocarcinoma perihilar bile duct cancer and distal bile duct cancer, according to location. The variability in location reflects the different morphologies and molecular alterations. In particular, intrahepatic peripheral mass forming cholangiocarcinoma is represented by the “small duct type” cholangiocarcinoma, which is different from the “large duct type” cholangiocarcinoma that, although intrahepatic, behaves similar to extrahepatic bile duct cancers, perihilar and distal ones. Recently, molecular targetable alterations, mainly FGFR2 fusions and IDH1 mutations, have been described, mostly in the intrahepatic “small duct type” subgroup and have opened the way, together with rarer targetable alterations, for personalisation of therapy also in these aggressive neoplasms.