Differential Contributions of BRCA1 and BRCA2 to Early-Onset Breast Cancer

Studies of large families many of whose members have cancer have led to the identification of two genes, BRCA1 and BRCA2, that, when mutated, predispose family members to breast cancer. 1 – 4 Members of such kindreds who are heterozygous carriers of a germ-line mutation have a high probability of breast cancer. 5 , 6 Families in which breast cancer is linked to a BRCA1 mutation also have increased susceptibility to ovarian cancer, 1 and families in which the link is to a BRCA2 mutation include cases of male breast cancer. 7 As in other syndromes involving a predisposition to cancer, familial cases of breast cancer . . .