ESR1 and breast lobular carcinoma: In univariate analysis (S1 Table), we observed that African American (vs. White), age<50 yrs, Northern plains (vs. East) area, divorced/separated/single/widowed (vs. married), infiltrating ductal carcinoma (vs. lobular carcinoma), higher T-stage, higher N-stage, negative ER, negative PR, higher tumor grade, modified radical mastectomy (vs. simple mastectomy), radiotherapy, and tissue reconstruction (vs. implant) were all associated with decreased BCSS.