(CNN) - More than 60% of all women over 40 in the United States have had a mammogram in the past two years. And 20% of mammograms detect something called ductal carcinoma in situ, or DCIS -- also known as Stage 0 breast cancer.
According to the American Cancer Society, more than 60,000 cases of DCIS are diagnosed every year. But it doesn't mean breast cancer.
DCIS are abnormal cells found inside the milk ducts of the breast. They can look like invasive breast cancer cells, but they haven't spread into the breast tissue -- and in some cases may not. Doctors treat DCIS one of three ways: with a lumpectomy, removing the masses themselves; lumpectomy and radiation; or removing the breast altogether with a mastectomy.