ERBB2 and breast cancer: These are: the luminal subtype A presenting high expression of ER and PR receptors without HER2 overexpression and low cell proliferation index, the luminal subtype B (ER+, PR±, HER2±, and high proliferation index), HER2 enriched tumours (ER-/PR- and HER2+), and finally the triple-negative BC subgroup or TNBC (ER-/PR- and HER2-)[8].