BRCA1 and breast cancer: Mutations in BRCA1 and BRCA2, which have been reported in various studies, account for 70-80 % and 15 % of families with a history of OC, respectively.[31, 32] Women with a familial history of OC are more likely to develop a deleterious mutation in BRCA1/2.[28] BRCA1 mutations typically confer a higher risk of BC and OC than BRCA2 mutations.