SMAD4 and intrahepatic cholangiocarcinoma: These include fibroblast growth factor receptor-2 (FGFR2) fusion and IDH1/2 in intrahepatic CCA (ICC); HER2 (erbB-2), PRKACA, and PRKACB in extrahepatic CCA (ECC: perihilar and distal CCA); EGFR, ERBB3, and PTEN in gallbladder cancer; and KRAS, SMAD4, and TP53 shared in ICC and ECC [13,14].