ERBB2 and neoplasm: As expected, expression of the oestrogen (ESR1)/progesterone (PGR) and HER2 (ERBB2) genes were highest in the luminal and HER2-enriched subtypes respectively, and as shown by others [37], expression of PGR was lower in luminal B tumours relative to luminal A (Additional file 5: Figure S5, “PGR”, P <  0.001).