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Epidemiology and Etiology
Breast cancer is the most common cancer in women in developed countries and is expected to account for 30% of new cancers in women in 2018. Nearly 266,120 patients develop breast cancer per year in the United States, and less than 1% of cases are reported in men. BRCA1 and BRCA2 mutations are associated with a 57% and 49% cumulative risk of breast cancer by age 70, respectively.1 However, less than 10% of all breast cancers are attributable to mutations involving susceptibility genes. Alcohol consumption, early menarche, late menopause, nulliparity, postmenopausal obesity, hormone replacement therapy, and delayed first pregnancy are all risk factors for breast cancer. Women receiving mantle field radiation for Hodgkin disease also carry a higher lifetime risk.