Targeted therapies have significantly improved the DFS of breast cancer patients, including patients with ER+ or HER2+ breast cancers, and these therapies hold promise for triple-negative breast cancer (TNBC), particularly when used in combination.36, 37 For HER2+ breast cancer, clinically approved therapies include the monoclonal antibodies trastuzumab and pertuzumab and, for third- or fourth-line therapy of metastatic disease, the small molecule lapatinib. The gene discussed is ERBB2; the disease is metastatic neoplasm.