For patients with HER2-positive breast cancer, positive lymph nodes (cN1), or a tumor size of 2cm or more, the Association of Breast Surgeons in the UK (ABS) suggests administering adriamycin and cyclophosphamide (AC) or epirubicin and cyclophosphamide (EC) in a dose-dense (3 weeks) fashion, followed by paclitaxel (or docetaxel) plus trastuzumab plus pertuzumab as neo-adjuvant chemotherapy (NACT). This evidence concerns the gene ERBB2 and breast cancer.