HER2 overexpression is also observed in 4.8% (95% confidence interval [CI] 0–14.5%) of ICC, 17.4% (95% CI 3.4–31.4%) of ECC, 19.1% (95% CI 11.2–26.8%) of gallbladder cancer, and 27.9% (95% CI 0–60.7%) of ampullary carcinoma [29]. Here, ERBB2 is linked to gallbladder cancer.