ESR1 and breast cancer: In case-series analyses, high levels of serum 25OHD were less likely to be associated with premenopausal breast cancer with poor prognostic characteristics than low levels (grade III versus I/II, OR = 0.45, 95% CI = 0.22–0.91; ER negative versus positive, OR = 0.48, 95% CI = 0.21–0.93; triple negative versus luminal A subtype, OR = 0.26, 95% CI = 0.09–0.71) (Figure 2).