Cancer is a group of diseases which causes cells in the body to change and grow out of control.
Most cancers are named after the part of the body where they first begin. Breast cancer begins in the breast tissue. The breast is made up of lobules, ducts and fatty, connective and lymphatic tissue. Incidence rates for breast cancer in the United States leveled off in the 1990s to 110.6 cases per 100,000 women, after rising 4 percent each year during the 1980s. An estimated 192,000 new cases of invasive breast cancer will be diagnosed in women in the year 2001.