Clinical Significance

Carcinoembryonic antigen (CEA) describes a set of highly-related glycoproteins involved in cell adhesion. CEA is normally produced in gastrointestinal tissue during fetal development, but the production stops before birth. Consequently, CEA is usually present at very low levels in the blood of healthy adults (about 2–4 ng/mL). However, the serum levels are raised in some types of cancer, which means that it can be used as a tumor marker in clinical tests. Serum levels can also be elevated in heavy smokers.
CEA is a protein produced by normal cells that is overexpressed, or produced in much higher amounts, in some cancers known as adenocarcinomas. CEA may be found in blood, urine, stool, and other bodily fluids, as well as in a tumor itself. It is more likely to be produced by slow-growing, well-differentiated tumors (tumors made up of cancer cells that appear very similar to normal cells) than by poorly differentiated tumors.