BRCA2 interacts with a signaling pathway that regulates fibroblast growth factors, and mutations are associated with a wider variety of breast cancer phenotypes than BRCA1 mutations.37 Double heterozygosity involving BRCA1 and BRCA2 mutations have been reported in the literature,38 though was not more penetrant than BRCA1 mutation alone. Here, BRCA1 is linked to breast cancer.