Due to the high intratumoral heterogeneity of gastric carcinoma and the focal nature of HER2 staining in up to 30% of cases (Bang et al. 2010; Rüschoff et al. 2010, 2012; Warneke et al. 2013), the experts recommend taking biopsies from different areas of the tumor to ensure that representative material is obtained sufficiently and to avoid false negative results. This evidence concerns the gene ERBB2 and neoplasm.