Human epidermal growth factor receptor 2 (HER2) overexpression has been observed in approximately 20% of breast cancer cases, and numerous other solid tumors with a frequency ranging from 2% to more than 50%, including gastric cancer, biliary tract cancer, colorectal cancer, non-small-cell lung cancer, uterine cancer and bladder cancer1. Here, ERBB2 is linked to biliary tract neoplasm.