HER2-targeted antibody-based drugs (e.g., trastuzumab, pertuzumab, ado-trastuzumab emtansine, and fam-trastuzumab-deruxtecan-nxki) and small molecule kinase inhibitors (e.g., lapatinib, neratinib, and tucatinib) have been approved for the treatment of HER2+ breast cancer. This evidence concerns the gene ERBB2 and breast cancer.