ERBB2 and neoplasm: Surrogate molecular tumour subtype was a strong prognostic factor; unadjusted 5‐year BCSS rates were 73 per cent in TNBC, 87 per cent in HR–/HER2+, 90·6 per cent in HR+/HER2– and 100 per cent in HR+/HER2+ subtypes (P < 0·001).