BRCA1 and breast cancer: Noteworthy, when assessing BRCA1 epimutations in non-TNBC breast cancers [31], BRCA1 hypermethylation was frequently observed in the small group of so-called ER-low tumors (tumors revealing ER immunostaining between 1% and 10%), which has been shown to have gene expression signatures mirroring TNBC [35].