It is estimated that 1 in 8 women will have breast cancer at some point in their life. Alterations in the BRCA1 and BRCA2 genes increase the risk of developing breast and ovarian cancer, as well as pancreatic cancer, melanoma and prostate cancer.
Some 70% of breast cancers are sporadic (they do not have an underlying hereditary cause). Between 20 and 25% of cases show familial aggregation (presence of more cases than expected in a family, but without finding a clear cause). Only between 5 and 10% of cases show a clearly hereditary cause (a mutation).
Women who are carriers of pathogenic mutations in BRCA1 or BRCA2 have a higher risk (up to 80% higher) than women who are not carriers, although the disease does not always occur.