Experimental Factor Ontology identifier EFO_0005760 (serum carcinoembryonic antigen measurement) can be described as follows. Quantification of carcinoembryonic antigen in serum. Carcinoembryonic antigen is a cancer-specific antigen associated with both tumors and the developing fetus. The main use of this antigen is as a tumor marker, especially with respect to intestinal cancers. Production of the antigen ceases shortly before birth, but may reappear in people who develop certain types of cancer.