For example, alterations in TP53, KRAS, BAP1, ARID1A, IDH, and SMAD4 are generally observed in intrahepatic cholangiocarcinoma, whereas TP53, KRAS, SMAD4, and ERBB2 mutations are associated with extrahepatic cholangiocarcinoma [22,26]. Here, SMAD4 is linked to intrahepatic cholangiocarcinoma.