ERBB2 and biliary tract cancer: Genomic alterations of ERBB2, including amplifications and mutations, are identified in approximately 20% of biliary tract cancers, with a higher prevalence in extrahepatic cholangiocarcinoma and gallbladder carcinoma, accounting for approximately 15–20% of cases, while the incidence of such alterations in intrahepatic cholangiocarcinoma (ICC) is only 1–5% (Galdy et al. 2017).