Carcinoembryonic antigen (CEA) is a glycosyl phosphatidyl inositol (GPI)-cell surface anchored glycoprotein, first identified in tissue extracts from human colon tumors. The CEA family of genes is part of the immunoglobulin superfamily. In humans, the CEA family consists of 29 genes, 18 of which are normally expressed only during fetal development. Therefore, CEA is not detectable in the blood of healthy adults, but CEA expression is observed in many types of cancer.
The measurement of CEA levels has been used in diagnostic tests for colorectal carcinoma, gastric carcinoma, pancreatic carcinoma, lung carcinoma and breast carcinoma, and to detect cancer recurrence after surgical removal of tumors. CEA levels are also elevated in other disease, like ulcerative colitis, pancreatitis, cirrhosis, COPD, and Crohn's disease, as well as in smokers.