Breast cancer is a malignant proliferation of epithelial cells lining the ducts or lobules of the breast.  For women, the three most commonly diagnosed cancers are breast, lung, and colorectum, representing one-half of all cases; breast cancer alone is expected to account for 29% all new cancer diagnoses in women.  It is estimated that 252,710 cases of breast cancer will be diagnosed and 40,610 patients will die of the disease in the United States in 2017.