CEA is a monomeric glycoprotein (molecular weight approximately 180000 daltons) with a variable carbohydrate component of approximately 45‑60 %.
CEA, like AFP, belongs to the group of carcinofetal antigens that are produced during the embryonic and fetal period. The CEA gene family consists of about 17 active genes in two subgroups. The first group contains CEA and the N on‑specific C ross‑reacting A ntigens (NCA); the second group contains the P regnancy‑ S pecific G lycoproteins (PSG). CEA is mainly found in the fetal gastrointestinal tract and in fetal serum. It also occurs in slight quantities in intestinal, pancreatic, and hepatic tissue of healthy adults. The formation of CEA is repressed after birth, and accordingly serum CEA values are hardly measurable in healthy adults. High CEA concentrations are frequently found in cases of colorectal adenocarcinoma. Slight to moderate CEA elevations (rarely >10 ng/mL) occur in 20‑50 % of benign diseases of the intestine, the pancreas, the liver, and the lungs (e.g. liver cirrhosis, chronic hepatitis, pancreatitis, ulcerative colitis, Crohn's Disease, emphysema). Smokers also have elevated CEA values.
The main indication for CEA determinations is the follow - up and therapy - management of colorectal carcinoma. CEA determinations are not recommended for cancer - screening in the general population. CEA concentrations within the normal range do not exclude the possible presence of a malignant disease