These tests look for tumor markers, sometimes called cancer markers, in the blood, urine or body tissues. Tumor markers are substances made by cancer cells or by normal cells in response to cancer in the body. Some tumor markers are specific to a type of cancer. Others can be found in several types of cancer.
These tests are most often performed on people who have already been diagnosed with cancer. Tumor markers can help you tell if your cancer has spread, if your treatment is working, or if your cancer has come back after you stop treatment.