Patients with HER2-positive breast cancer who still have metastatic axillary lymph nodes after PST benefit significantly from an adjuvant switch from anti-HER2 therapy to trastuzumab emtansine (T-DM1) in terms of invasive disease-free survival (DFS) compared with continuation of trastuzumab therapy started neoadjuvantly [19]. This evidence concerns the gene ERBB2 and breast cancer.