However, the introduction of HER2-targeted therapies such as trastuzumab (Herceptin; Roche), pertuzumab (Perjeta; Roche) and the antibody–drug conjugate (ADC), trastuzumab-emtansine (T-DM1, Kadcyla; Roche) and the small molecule HER2/EGFR tyrosine kinase inhibitor (TKI), lapatinib (Tykerb; Novartis) have improved the outcome of patients with HER2-positive BC, including those with metastatic disease (Swain et al. 2015; Verma et al. 2012; Geyer et al. 2006). Here, ERBB2 is linked to breast cancer.