Breast cancer is the second leading cause of cancer death in women. It is characterized by the abnormal growth and uncontrolled division of cells in the breast. Cancer cells form a tumor, that is often felt as a lump in the breast. This tumor can invade and destroy surrounding normal tissue, and can spread (metastasize) cancer cells throughout the body via the bloodstream or lymph system.

Every woman is at risk for breast cancer. If she lives to be 85, there is a one out of nine chance that she will develop the condition sometime during the rest of her life. As a woman ages, her risk of developing breast cancer rises dramatically regardless of her family history. The breast cancer risk of a 25-year-old woman is only one out of 19,608; by age 45, it is one in 93. In fact, 80% of all breast cancers...