ERBB2 and neoplasm: IHC for hormone receptor status, human epidermal growth factor receptor-2 (HER2) status, and at least one basal marker (cytokeratin [CK]5/6 or epidermal growth factor receptor [EGFR]) enable the division of tumours into Luminal 1, Luminal 2, Non-luminal HER2 positive tumours, and triple negative tumours (Fig. 5) and are associated with different behaviour [7].