The common genetic alterations in ICC include TP53 (30%), KRAS (24%), ARID1A (20%), IDH1 (18%) and MCL1 (16%), whereas for extrahepatic CCA, common aberrations include TP53 (45%), KRAS (40%), ERBB2 (20%), SMAD4 (25%), F-box/WD repeat-containing protein 7 (FBXW7) (15%) and CDKN2A (15%). The gene discussed is SMAD4; the disease is cholangiocarcinoma.