Per the HER2 observations and its marked intratumoral heterogeneity (Fig. 2) (Warneke et al. 2013a, b), experts from an interdisciplinary German group accepted GC-specific HER2 testing protocols and recommended a minimum of five tumor-bearing biopsies from the primary site of the tumor growth (Baretton et al. 2016). This evidence concerns the gene ERBB2 and neoplasm.