Cancer that starts in the lining of the duct but does not grow through the walls of the duct into the surrounding breast tissue and beyond is called ductal carcinoma in situ (DCIS). The cancer cells cannot spread to the lymph nodes (small, oval-shaped tissues containing certain infection-fighting immune system cells) or other organs. Ductal carcinoma in situ can go on to become invasive cancer. It is sometimes called a precancer. Almost all women diagnosed with ductal carcinoma in situ can be cured. Many cases are caught by mammograms.