ERBB2 and intrahepatic cholangiocarcinoma: Isocitrate dehydrogenase gene (IDH) mutations and fibroblast growth factor receptor 2 (FGFR2) fusions are found almost exclusively in intrahepatic cholangiocarcinomas, with frequencies of approximately 15% and 20% respectively [33,34,35,36,37], whereas human epidermal growth factor receptor-2 gene (HER2) aberrations are observed in approximately 15% of cases of extrahepatic cholangiocarcinomas and gallbladder carcinomas [38].