ERBB2 and breast cancer: In recent years, however, two HER2-targeted antibody–drug conjugates (ADCs), trastuzumab deruxtecan (T-DXd) (10) and trastuzumab duocarmazine (SYD985) (11), have shown promising antitumor activity in patients with HER2-low breast cancer, thus offering novel therapeutic options for HER2-low tumors and shifting the attention of physicians toward this particular subset of patients (12, 13).