ERBB2 and breast cancer: The IHC describes five surrogates BC subtypes: (1) luminal A; (2) luminal B HER2 negatives; (3) luminal B HER2 positive; (4) HER2 positives non luminal (corresponding to Erb-B2 overexpression in the intrinsic type classification) and (5) triple negative (the basal-like type of intrinsic subtyping).