In the context of HER2-positive breast cancer, the strong antitumor immune response driven by anti-HER2 antibodies—mediated through antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP)—may reduce the potential benefit of adding anti-PD-L1 antibodies to standard therapy [141]. This evidence concerns the gene ERBB2 and breast carcinoma.