ESR1 and breast carcinoma: There are two possible explanations: First, the E-MTAB-365 ER-positive sub-cohort has relatively lower relapse rate compared to the exploration HRPBC cohort and GSE4922 ER-positive cohort (23.7% in E-MTAB-365 vs. 38.7% in exploration HRPBC and 36.0% in GSE4922) which may have hindered the discerning power of survival analysis; Second, in microarray datasets, gene expressions were analyzed using total tissue mRNA, and mRNA from cell types other than breast cancer cells may interfere with the expression of certain genes.