There are 2 types of breast carcinoma in situ: ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS). DCIS is a noninvasive condition in which abnormal cells are found in the lining of a breast duct (a tube that carries milk to the nipple). The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, DCIS may become invasive cancer and spread to other tissues, although it is not known how to predict which lesions will become invasive cancer. LCIS is a condition in which abnormal cells are found in the lobules (small sections of tissue involved with making milk) of the breast. This condition seldom becomes invasive cancer; however, having LCIS in one breast increases the risk of developing breast cancer in either breast. Also called stage 0 breast carcinoma in situ.