ERBB2 and breast cancer: While it is not yet clear which IHC markers (e.g., CK5, CK5/6, CK14, CK17 and/or EGFR), alone or in combination, provide the greatest accuracy in defining basal-like BC, Chung et al. [23] have recently described that 37% of 97 patients with stage 1-3 HER2+ BC expressed at least one basal marker.