ERBB2 and breast cancer: Current FDA-approved treatments for HER2 overexpressed or gene amplified (HER2+) breast cancers have significantly improved clinical outcomes in the metastatic and adjuvant settings and include small-molecule kinase inhibitors, such as lapatinib (Tykerb), monoclonal antibodies, such as trastuzumab (Herceptin) and pertuzumab (Perjeta), and antibody-drug conjugates, such as ado-trastuzumab emtansine (Kadcyla) [2, 3].