KM curves combining all three cohorts suggested the same tendency, where 23-gene signature-based ER negative but IHC based ER positive tumours were associated with a poorer clinical outcome compared to ER positive tumours predicted by both methods (HR = 2.20, 95% CI: 1.40–3.30, P = 0.00035) (Figure 4b). This evidence concerns the gene ESR1 and neoplasm.