HER2 positivity (overexpression [IHC3+] and/or gene amplification [FISH positive]) has been reported in 22% of advanced G/GEJ cancers but varies by tumor location and type in ToGA study, where HER2 staining (≤30% stained cells) by IHC was observed in almost 50% of cases.14 This evidence concerns the gene ERBB2 and cancer.