ERBB2 and breast cancer: Hormone receptor-negative (HRneg) breast cancer accounts for 30% to 40% of all newly diagnosed breast malignancies and is clinically subdivided into either human epidermal growth factor receptor 2 (HER2/ERBB2)-positive or triple-negative (Tneg) breast tumors, and about 60% of the latter consist of basal-like breast cancers [1-4].