In a Japanese study, the positive rate of HER2 varies among different subtypes of cholangiocarcinoma: 3.7% for intrahepatic cholangiocarcinoma, 3% for proximal extrahepatic cholangiocarcinoma, 18.5% for distal extrahepatic cholangiocarcinoma, 31.3% for gallbladder carcinoma, and 16.4% for ampulla carcinoma (45). The gene discussed is ERBB2; the disease is intrahepatic cholangiocarcinoma.