BRCA1 and BRCA2 mutations in a population-based study of male breast cancer

We have carried out a population-based study of 94 MBC cases collected in the UK. We screened genomic DNA for mutations in BRCA1 and BRCA2 and used family history data from these cases to calculate the risk of breast cancer to female relatives of MBC cases. We also estimated the contribution of BRCA1 and BRCA2 to this risk.Nineteen cases (20%) reported a first-degree relative with breast cancer, of whom seven also had an affected second-degree relative. The breast cancer risk in female first-degree relatives was 2.4 times (95% confidence interval [CI] = 1.4–4.0) the risk in the general population. No BRCA1 mutation carriers were identified and five cases were found to carry a mutation in BRCA2. Allowing for a mutation detection sensitivity frequency of 70%, the carrier frequency for BRCA2 mutations was 8% (95% CI = 3–19). All the mutation carriers had a family history of breast, ovarian, prostate or pancreatic cancer. However, BRCA2 accounted for only 15% of the excess familial risk of breast cancer in female first-degree relatives.These data suggest that other genes that confer an increased risk for both female and male breast cancer have yet to be found.Male breast cancer (MBC) is a rare disease and little is known about its aetiology. However, female first-degree relatives of MBC cases are at increased risk of breast cancer [1,2,3,4,5,6], which suggests that there is an inherited component to the disease. Several genes that are associated with a high lifetime risk of breast cancer in women have been identified during the past decade. One of these, BRCA2, has also been shown to confer a significant risk of breast cancer in men, and a recent study found the risk of breast cancer in male BRCA2 mutation carriers from multiple case breast/ovarian cancer families to be 80-fold higher than in the general population [7]. This equates to a 7% risk of breast cancer by age 80. The prevalence of BRCA2 mutations in MBC cases unselected for family history has been estimated in