ERBB2 and breast cancer: Trastuzumab, a humanized monoclonal antibody targeted against epidermal growth factor receptor 2 (HER2), was approved by the United States Food and Drug Administration (FDA) for the clinical management of HER2-positive breast cancers either as an adjuvant or neoadjuvant, and metastatic breast and gastric carcinomas and metastatic gastric cancer [1].