ERBB2 and gastric adenocarcinoma: It is well known that 8–30% gastric adenocarcinomas (GA) show HER2 overexpression or gene amplification (Aditi et al. 2016; Bang et al. 2010; Cordero-García et al. 2019; Qiu et al. 2017; Shen et al. 2016; Shitara et al. 2013).