ERBB2 and breast cancer: In HER2+ breast cancer, ado-trastuzumab-emtansine (T-DM1) is approved as adjuvant treatment for patients with residual disease after neoadjuvant therapy (von Minckwitz et al., 2019), and is still the standard of care as second-line treatment for HER2+ advanced breast cancer according to the results of TH3RESA and EMILIA trials (Diéras et al., 2017; Krop et al., 2017).