Increases in risk were found for known risk factors such as decreased age at menarche and a family history of breast cancer. No change in risk was observed with single marital status, nulliparity, premenopausal status, or lactation. Chu sy, lee nc, wingo pa, senie rt, greenberg rs, peterson hb. The relationship between body mass and breast cancer among women enrolled in the cancer and steroid hormone study. Breast cancer risk factors among black women and white women similarities and differences. Methods we pooled questionnaire data on black women from three case-control studies (womens contraceptive and reproductive experiences, carolina breast cancer study, and womens circle of health study) and nested case-control data from the prospective black womens health study for an analytic sample of 5,015 invasive breast cancer cases and 15,354 controls 15. black women under the age of 45 are at increased risk for an aggressive form of breast cancer estrogen receptor (er) negative if they experienced a high number of pregnancies, never breast fed, andor had higher waist-to-hip ratio. These findings appear in cancer epidemiology, biomarkers, & prevention. Breast cancer has the highest mortality rate of any cancer in women between the ages of 20 and 59. African american women have a 31 breast cancer mortality rate the highest of any u. Among women younger than 45, breast cancer incidence is higher among african american women than white women. our focus was to study breast cancer risk factors in african women, in particular, nigerian women. This is very important because of the peculiarity in african women. One of the peculiarities in african women is the difference in their risk factor profiles, including later menarche age and higher parity in comparison with women in high-income. research shows that racial and ethnic minority women with breast cancer are less likely to receive radiotherapy, which may contribute to a higher risk of dying from breast cancer. Compared with white women, black women with early-stage breast cancer are half as likely to be treated with radiotherapy. Black women with breast cancer are also more likely to experience delays in beginning radiotherapy compared with white women. overweight and obese women have a higher risk of being diagnosed with breast cancer compared to women who maintain a healthy weight, especially after menopause. Being overweight also can increase the risk of the breast cancer coming back (recurrence) in women who have had the disease.