Chowdhury M, et al. - Increased mammographic breast density is considered a significant risk factor for breast cancer, so researchers investigated if it was also a risk factor for the development of contralateral breast cancer. Data were drawn from Breast Cancer Surveillance Consortium and involved women diagnosed with invasive breast cancer or ductal carcinoma in situ between the ages of 18 and 88 from 1995 to 2009. Mammographic breast density, age of first breast cancer diagnosis, family history of breast cancer, anti-estrogen treatment, hormone replacement therapy, menopausal status, and estrogen receptor status, all from the time of first breast cancer diagnosis, were the included risk factors in the study. For the development of contralateral breast cancer, breast density was an independent and significant risk factor and this risk factor should contribute to clinical decision making.