Carcinoma In Situ (CIS) is a term used to describe a group of abnormal cells that are found in the lining of a specific organ but have not invaded surrounding tissues. These cells are considered pre-cancerous, meaning they have the potential to develop into invasive cancer if not treated. CIS can occur in various parts of the body, including the breast, cervix, and skin. Diagnosis of carcinoma in situ typically involves imaging tests and biopsies. Treatment options may include surgery, radiation therapy, or close monitoring, depending on the location and characteristics of the abnormal cells. Early detection and intervention are crucial for preventing progression to invasive cancer.