The diversity of clinically HER2 + tumours has been reported previously; using PAM50 only 64% are assigned to the HER2-enriched group, the remainder distributing across all intrinsic subtype categories.31,32 Clinical HER2 status was shown to be non-contributory to prognosis after intrinsic subtype categorisation.31 Our findings provide a further example of the added value of molecular tumour subtyping in identifying tumours where HER2 is the primary molecular driver regardless of clinical HER2 status. The gene discussed is ERBB2; the disease is neoplasm.