What is DCIS?
DCIS, or ductal carcinoma in situ, is a pre-cancerous condition in which abnormal cells are confined to the milk ducts in the breast. These tumors show no evidence of microscopic invasion to the surrounding breast tissues. DCIS is usually found as microscopic calcifications on a mammogram. Since DCIS is a pre-cancerous condition, it can become an invasive cancer if left untreated.