Since RANK/RANKL critically influence Brca1 mutation-driven breast carcinogenesis in mice, we assessed the role of genetic modifiers of breast cancer risk in women with inherited BRCA1 mutations at the corresponding locus encoding for human RANK, TNFRSF11A. This analysis was performed using data from the Collaborative Oncological Gene-environment Study (iCOGS) that included 51 TNFRSF11A single-nucleotide polymorphisms (SNPs) genotyped in ∼15 200 BRCA1 and ∼8 200 BRCA2 mutation carriers21,22 (Supplementary information, Table S2). This evidence concerns the gene BRCA1 and breast cancer.