Carcinoembryonic antigen (CEA) is a glycoprotein
involved in cell adhesion. It is normally produced
during fetal development, but the production of
CEA stops before birth. Therefore, it is not usually
present in the blood of healthy adults, although
levels are raised in heavy smokers. CEA is synthesized
during development in the fetal gut, and is
re-expressed in increased amounts in Intestinal
Carcinomas and several other tumors.
CEA is employed essentially as a tool to assist in
the distinction between Adenocarcinoma and
Malignant Mesotheliomas of the epithelial type,
along with other markers for mucosubstances
such as Leu M1 and Ber-EP4. Another suggested
use of CEA is the immunophenotyping of various
Metastatic Adenocarcinomas as a means of identifying
their origin.