ERBB2 and breast cancer: Additionally, the discovery of 6 intrinsic biological BC subtypes (luminal A; luminal B; HER2-enriched; basal-like; normal breast-like; and claudin-low) (Perou et al. 2000; Sorlie et al. 2001; Carey et al. 2006; Prat et al. 2010) has reshaped our understanding of disease biology and shifted our current approach to treatment.