ERBB2 and gastric cancer: Second, intratumoral HER2/HER2 heterogeneity was not evaluated in our study, which might result in bias of accurate assessment of HER2/HER2 status due to the fact that intratumoral HER2/HER2 heterogeneity is particularly significant in GC, ranging from 6 to 69% of HER2-postive GC patients and predicts unfavorable prognosis in HER2-positive GC (Grillo et al. 2016; Kaito et al. 2019).