A further meta-analysis of 11 studies of eCCA found a mean HER2 overexpression rate (defined as moderate/strong IHC staining) of 17.4% (95% CI 3.4–31.4%) by IHC, with an HER2 amplification rate by in-situ hybridisation of 57.6% among tumours with moderate/strong expression by IHC [31]. This evidence concerns the gene ERBB2 and neoplasm.