Many other solid tumors exhibit high levels of HER2 expression, including gastric cancer, urothelial carcinoma, lung cancer and biliary tract cancer (BTC), and anti-HER2 drugs have exhibited great therapeutic benefits in clinical settings (Lamberti et al., 2020; Mollica et al., 2020; Ricci et al., 2021; Rizzo et al., 2021). Here, ERBB2 is linked to biliary tract cancer.