Numerous risk factors for breast cancer in women have been identified, including age, personal history of certain benign breast diseases or breast cancer, early menstruation or late menopause, never having been pregnant or having a first pregnancy after age 30, use of oral contraceptives, family history of breast cancer, presence of certain genetic mutations (BRCA1 and BRCA2), history of radiation therapy to the chest, long-term use of combined hormone therapy, use of DES (diethylstilbestrol), increased breast density, alcohol use and obesity after menopause. This evidence concerns the gene BRCA1 and breast cancer.