Both the BRCA1 and BRCA2 genes are important in suppressing tumors and repairing damaged DNA. Mutations in the BRCA1 and BRCA2 genes give rise to a predisposition to cancer which is referred to as Hereditary Breast and Ovarian Cancer (HBOC) syndrome. While more than 500 different mutations can occur in the BRCA1 gene on chromosome 17 and raise a woman's risk for breast cancer, there are also more than 300 potential mutations of the BRCA2 gene on chromosome 13 that are associated with HBOC.
There is an increased risk of getting certain types of cancer in the presence of BRCA1 or BRCA2 mutations but not everyone who has a gene mutation will develop cancer. A woman with a BRCA1 or BRCA2 gene mutation has a 50 to 85% chance of developing breast cancer. This compares with only a 10 to 12% risk among women in the general population. In addition, the presence of a BRCA1 or BRCA2 gene mutation along with a history of breast cancer puts a woman at a 40 to 60% risk of developing a second primary breast cancer. Furthermore, a woman with a BRCA1 mutation has a 20 to 54% chance of developing ovarian cancer, compared with only a 1 to 2% risk among women without the mutation. In the case of a BRCA2 gene mutation, this risk is 10 to 27%.
Mutations in men
Men who have a BRCA1 gene mutation have a slightly increased risk for breast and prostate cancer. Those with a BRCA2 gene mutation have around a 6-10% risk of developing breast cancer, compared with a less than 1% risk in men without a BRCA2 mutation. The risk of developing other cancers such as prostate cancer and pancreatic cancer, is also slightly raised in men with a BRCA2 mutation.