Several HER2-targeting agents are available for the treatment of early, advanced and metastatic HER2+BC, and include monoclonal antibodies (trastuzumab, pertuzumab), tyrosine kinase inhibitors (lapatinib, neratinib), and ADCs (trastuzumab-trastuzumab-TDM1 and trastuzumab deruxtecan). This evidence concerns the gene ERBB2 and breast cancer.