ESR1 and breast cancer: For the T allele of rs4784227, positive associations with BC risk were found in postmenopausal (OR = 1.44, 95%CI = 1.11–1.87), ER positive (OR = 1.21, 95%CI = 1.02–1.42) and PR positive (OR = 1.22, 95%CI = 1.01–1.49) subjects, as compared to the premenopausal, ER negative and PR negative subgroups (OR = 1.02, 95%CI = 0.82–1.27, OR = 1.10, 0.89–1.38, and OR = 1.09, 95%CI = 0.87–1.37, respectively).