ESRRA and breast cancer: Our findings pointed out that (a) ERRα plays a role in vitamin D metabolism and sensitivity in breast cancer, (b) the ERRα/VDR axis is at the crossroads of estrogen signaling activation, and (c) the simultaneous overexpression of ERRα, VDR, and CYP24A1 is correlated with poor prognosis in basal‐like breast cancer.