ERBB2 and breast cancer: BC is commonly divided into three groups, 1) luminal BC that express the oestrogen (ER) and progesterone (PR) receptors, 2) basal BC that overexpress human epidermal growth factor receptor 2 (HER2), and 3) basal triple-negative BC (TNBC) that does not express any of the three receptors (Figure 1) (Goldhirsch et al., 2011; Uscanga-Perales et al., 2019).