ERBB2 and cancer: Based on molecular profiling (Yersal and Barutca, 2014, Sotiriou and Pusztai, 2009), these cancers generally fall into two subtypes: (1) HER2-enriched tumors (those with overexpression or amplification of human epidermal growth factor receptor 2 [HER2]) and (2) basal-like tumors (which generally do not express estrogen or progesterone receptors or HER2/neu, but have high levels of basal markers and/or epidermal growth factor receptor expression and a high rate of TP53 mutations) (Sorlie et al., 2001, Perou et al., 2000).