Trastuzumab resistant breast cancers circumvent HER2 inhibition via bypass signaling and activation of downstream pathways independent of HER2 (Normanno et al., 2006; Bender and Nahta, 2008; Hynes and MacDonald, 2009; Weigelt et al., 2010; Wilken and Maihle, 2010; Brünner-Kubath et al., 2011; Nahta, 2012; Vu and Claret, 2012; Wong and Lee, 2012). This evidence concerns the gene ERBB2 and breast cancer.