For women with HER2-positive (HER2+) metastatic disease, trastuzumab, a humanized monoclonal antibody directed against the extracellular domain of HER2 (Valabrega et al. 2007), combined with recently approved pertuzumab and a taxane (docetaxel or paclitaxel) are recommended as first-line therapy (National Comprehensive Cancer Network 2015; Giordano et al. 2014). The gene discussed is ERBB2; the disease is metastatic neoplasm.