Antigen present only in very small amounts in normal tissues. Used as a screening test for cancer and as a tool to monitor the success of therapy (e.g., surgery, radiotherapy, chemotherapy).
An antigen measured in serum and sometimes other body fluids to detect the presence or recurrence of cancer in such sites as the colon, pancreas, lung, breast, or prostate.
A protein originating from the fetus, which exhibits elevated levels in the blood in association with certain types of cancer, such as breast or digestive-system cancers.