Data from eight breast cancer genome-sequencing projects have identified 25 patients with HER2 somatic mutations in cancers lacking HER2 gene amplification (Kan et al., 2010; Banerji et al., 2012; Shah et al., 2012; Stephens et al., 2012; Bose et al., 2013). The gene discussed is ERBB2; the disease is breast cancer.