Recently, gene expression profiling analyses using DNA microarrays and later on immunohistochemical (IHC) studies have enabled the recognition of distinct subtypes of tumours associated with different clinical outcomes [3–5]: luminal A (positive for oestrogen receptor (ER) and progesterone receptor (PR) and negative for human epidermal growth factor receptor type 2 [HER2]); luminal B (ER+, PR+, HER2+); HER2 overexpressing (ER-, PR-, HER2+); basal-like (differentiation towards basal cell types); unclassifiable or normal breast-like (tumours that are negative for all the markers above). Here, ERBB2 is linked to neoplasm.