Distal cholangiocarcinoma (dCCA), arising from the extrahepatic bile duct (ductus choledochus), and gallbladder carcinoma show overlapping molecular features, including KRAS mutations, ERBB2 amplification, BRCA1/2 alterations, and MSI-H in a minority of cases. The gene discussed is ERBB2; the disease is gallbladder carcinoma.