Navratilova said she has a noninvasive form of the cancer, called ductal carcinoma in situ, that was detected during a mammogram.

CNN: Martina Navratilova has breast cancer

Even in the precancerous stage, called ductal carcinoma in situ (DCIS) when abnormal cells are confined to a milk duct, physicians almost always advise women to have a lumpectomy or mastectomy along with radiation, because about 20% of the 65, 000 cases of DCIS found every year in the U.S. become invasive cancer.

WSJ: Can Breast Cancer Be Overtreated?