Definition

A condition in which abnormal cells are found in the tissues of the breast. There are 2 types of breast carcinoma in situ: ductal carcinoma in situ (DCIS) and Paget disease of the nipple. DCIS is a condition in which the abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. Paget disease of the nipple is a condition in which abnormal cells are found in the skin cells of the nipple and may spread to the areola. Patients with Paget disease of the nipple may also have DCIS or invasive breast cancer in the same breast. Also called stage 0 breast carcinoma in situ.