The frequency of HER2 amplification in BTC varies according to the primary tumor site, and is reported to be highest in gallbladder cancer and lowest in intrahepatic cholangiocarcinoma,28,31,36 which was confirmed in our study (3% in intrahepatic cholangiocarcinoma, 5% in extrahepatic cholangiocarcinoma, 27% in gallbladder cancer, and 14% in cancer of the ampulla of Vater). Here, ERBB2 is linked to intrahepatic cholangiocarcinoma.