Two autosomal dominant genes, BRCA1 and BRCA2,
account for most of the cases of familial breast cancer.
Women who carry a harmful BRCA mutation have a 60% to
80% risk of developing breast cancer in their lifetimes. Other
associated malignancies include ovarian cancer and
pancreatic cancer. If a mother or a sister was diagnosed breast
cancer, the risk of a hereditary BRCA1 or BRCA2 gene
mutation is about 2-fold higher than those women without a
familial history. Commercial testing for BRCA1 and BRCA2
gene mutations has been available in most developed
countries since at least 2004.