According to a recent estimate, 13% of women in the United States will develop breast cancer during their lifetimes. Since early detection improves survival, the U.S. Preventive Services Task Force has recommended that women aged 40 and older be screened for breast cancer every 1 to 2 years. Mammography is considered the reference standard for breast cancer screening and the most effective means for detecting breast cancer when combined with breast self-examination. However, mammography has a large number of false-positive results. When biopsies are done on lesions identified by mammography, approximately three fourths of the lesions are benign. A better method of detecting breast cancer would prevent many women from having unnecessary biopsies.