Definition

A condition in which cells that look mostly like normal cells under a microscope are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. Grade I ductal carcinoma in situ tends to grow more slowly than grade II or grade III ductal carcinoma in situ. It is also less likely to come back or become invasive breast cancer and spread to other tissues. Also called grade I DCIS, low-grade DCIS, and low-grade ductal carcinoma in situ.