carcinoembryonic antigen (KAR-sih-noh-EM-bree-AH-nik AN-tih-jen)
A substance that may be found in the blood of people who have colon cancer, other types of cancer or diseases, or who smoke tobacco. Carcinoembryonic antigen levels may help keep track of how well cancer treatments are working or if cancer has come back. It is a type of tumor marker. Also called CEA.