ERBB2 and gastric adenocarcinoma: The molecular characterization of EAC is divided into four etiological/genetic subtypes based on gastric adenocarcinoma molecular characterization classification (Cancer Genome Atlas Research Network, 2014): (1) EBV-associated tumors; (2) Microsatellite instability (MSI) tumors commonly with PIK3CA, EGFR and human epidermal growth factor receptor 2 (HER2) mutations; (3) Genomically stable tumors, (4) Chromosomally instability (CIN) tumors with TP53 mutations as well as RTK/RAS, VEGFR, and p110 amplifications (Barsouk et al., 2019).