In addition to determination of the HER2 status, clinical practice guidelines currently also recommend evaluating the PD-L1 status—mostly using the CPS (number of positive tumor cells and immune cells) in the case of metastatic gastric carcinoma and/or esophageal carcinoma, also using the TPS, which describes the percentage of PD-L1-expressing tumor cells in relation to all tumor cells found on the respective tumor specimen (Lordick et al. 2022a; Obermannová et al. 2022; Nagtegaal et al. 2020). Here, ERBB2 is linked to neoplasm.