Aside from female gender, increasing age is the strongest risk factor for developing breast cancer. Consequently, younger women are at much lower risk even when compared with older premenopausal women. An average woman has a 1 in approximately 1,800 risk of developing breast cancer in her 20s, 1 in 230 in her 30s, and 1 in 70 in her 40s (4). Family history is the primary risk factor for developing breast cancer at young age, particularly when breast cancer has occurred in a first-degree relative at a young age. Although 5% to 10% of breast cancers are attributable to germ-line mutations such as BRCA1 and BRCA2 on chromosomes 17 and 13, respectively, another 15% to 20% of breast cancers are associated with the presence of gene polymorphisms and environmental factors (e.g., radiation; see later). By virtue of her age alone, a young woman diagnosed with breast cancer has a greater probability of carrying a BRCA mutation. In an unselected group of women under 40 having surgery for early breast cancer, 9% harbored a deleterious BRCA1 or BRCA2 mutation (26). Other factors, including a personal or family history of ovarian cancer, bilateral breast cancer, or Ashkenazi Jewish ancestry, may increase that risk. The meaning of an unknown variant of the BRCA1 or BRCA2 genes may also vary by race (27). Young women with breast cancer should consider genetic counseling and testing for BRCA1 and BRCA2, particularly if ...