ESR1 and breast cancer: The risk-of-recurrence (ROR) score derived from the Predictor Analysis of Microarray (PAM) 50 (Prosigna) is a 50 gene assay that describes individual breast cancers based on intrinsic subtype and has also been shown to be an independent prognostic factor for risk of local recurrence in post-menopausal ER+ early stage breast cancer patients [72,73,74].