ESR1 and breast cancer: The gene expression pooled proliferation score (CPS) from all these markers, showed that ER+ BC patients with AR/ER ratio ≥ 2 (defined by both IHC and qPCR methods) have significantly higher levels of proliferation (P < 0.001) compared to cases with AR/ER ratio < 2, even when only ER+/HER2- cases were taken into account (P < 0.05).