ERBB2 and gastric cancer: With the exception of administration of molecular targeted drugs for patients with HER-2 positive gastric cancer (Shitara et al., 2020), the majority of gastric cancer patients receive “one-size-fits-all” chemotherapy following various guidelines, which inevitably leads to huge differences and uncertainties in treatment responses in the individual patients (Petrelli et al., 2019; Tokunaga et al., 2020).