However, heterogeneously distributed clonal tumor cells also influence the diagnostic algorithm for determining the target protein on the tumor tissue: Previous studies on Her2/neu or PD-L1 demonstrated how many tumor-bearing biopsies are necessary to obtain a realistic picture of the Her2/neu- or PD-L1 status of the whole tumor: We could demonstrate that for a correct Her2/neu- and PD-L1 assessment of gastric adenocarcinomas a minimum of 5 (Her2/neu) and 4 (PD-L1) tumor-bearing biopsies are necessary12. This evidence concerns the gene ERBB2 and gastric adenocarcinoma.