Definition

A condition in which cells that look very different from normal cells under a microscope are found in the lining of a breast duct. There may also be areas of dead cells in the abnormal tissue. The abnormal cells have not spread outside the duct to other tissues in the breast. Grade III ductal carcinoma in situ tends to grow more quickly than grade I or grade II ductal carcinoma in situ and is more likely to come back or become invasive breast cancer and spread to other tissues. Also called grade III DCIS, high-grade DCIS, and high-grade ductal carcinoma in situ.