ESR1 and breast cancer: In our study, UGT2B15*2 A/C is likely to have a clinically significant impact on recurrence risk, CYP3A5∗3 A/G on endometrial hyperplasia, and SULT1A1∗2 G/A, and ESRA V364E on vaginal bleeding in Chilean patients with breast cancer who receive tamoxifen adjuvant therapy.