Gene expression profiling initially subcategorised tumours broadly into four subgroups, namely ‘luminal-like’ cancers that were predominantly oestrogen and progesterone receptor positive (ER+/PgR+), human epidermal growth factor receptor-2 (or HER2/neu) positive, ‘basal-like’ (ER−/PgR−/HER2− that is triple-negative breast cancer (TNBC)), and ‘normal-like’ cancers3. This evidence concerns the gene ERBB2 and cancer.