SMAD4 and gallbladder cancer: Alterations in IDH1 and FGFR2 genes were mostly noted among intrahepatic cholangiocarcinoma (iCCA) samples, TP53, ERBB2/HER2, and SMAD4 mutations were more frequent among gallbladder cancer (GBC) samples while extrahepatic cholangiocarcinoma (eCCA) more commonly harbored KRAS mutations (all Q < 0.001).