ESR1 and breast cancer: However, when evaluating the association between GPR30 staining on BC outcome with the cohort stratified for ER status (S3 Fig), we found a trend that both strong total GPR30 and PM-specific GPR30 staining associate with worse prognosis in ER-positive CBC (S2 Fig), suggesting that GPR30 adds prognostic information beyond ER, at least in ER-positive tumors.