ESR2 and breast cancer: Taken together with our result that neither ESR1 nor ESR2 expression did not correlate well with estrogen response within ER-positive subtype, we believe that the score may be a predictor than ESR1. Several prognostic scores have been developed in ER-positive patients using gene expression and clinical information, such as 21-gene Oncotype DX, 70-gene MammaPrint, 50-gene PAM50, 12-gene EndoPredict, and Breast Cancer index [19,20].