Breast cancer is the most common malignancy among women. Current estimates are that one in eight women born in 1990 will contract breast cancer by age 85. Many factors contribute to breast cancer risk. Inheritance of breast cancer susceptibility genes contribute to approximately 5-10% of all breast cancers. The breast/ovarian cancer susceptibility gene BRCA1 has been identified on chromosome 17. Women who inherit certain BRCA1 mutations have an 80% risk of breast cancer.