The introduction of HER2-directed therapies, most notably, trastuzumab, pertuzumab, ADCs such as trastuzumab emtansine (T-DM1) and T-DXd, and TKIs such as lapatinib, neratinib, pyrotinib, and tucatinib, has shown improvements in the prognosis of patients with HER2+ metastatic BC. The gene discussed is ERBB2; the disease is breast cancer.