Based on the previous findings, we tried to clarify the prevalence of constitutional epimutations in BC and OC predisposition by analyzing the methylation status of BRCA1 and RAD51C promoters in 108 women affected by BC and/or OC, with high a priori risk of harboring pathogenetic variants at BRCA1 and who tested negative for BRCA sequence variants. This evidence concerns the gene RAD51C and breast cancer.