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Definition of Carcinoembryonic Antigen
A protein present in the blood circulation with certain types of cancer. In this regard, Carcinoembryonic antigen (CEA) serves as a tumor marker. The cancers associated with elevated blood CEA levels are carcinomas of the colon and rectum (colorectal cancer), pancreas, stomach, breast, and lung.
The developing fetus also produces CEA, as do benign (noncancerous) tumors of the gastrointestinal tract. In these circumstances the presence of CEA in the blood circulation is normal and not an indication of cancer.