Tumor Markers

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What are tumor markers?

Tumor markers are substances that can be found in the body when cancer is present. Ideally, a tumor marker would always be found in the blood in higher-than-normal amounts, but only when a certain type of cancer is present. In reality, tumor markers are rarely like that.

Some tumor markers are found in blood, but others are found in urine or other body fluids. Still others are found in tumors and other tissues. They may be made by the cancer cells themselves, or by the body in response to cancer or other conditions. Most tumor markers are proteins, but some newer markers are genes or other substances.

There are many different tumor markers. Some are linked only to one type of cancer, while others can be found in many cancers.

To test for a tumor marker, the doctor most often sends a sample of the patient’s blood or urine to a lab. Sometimes a piece of the tumor itself is tested for tumor markers.

Tumor markers alone are rarely enough to show that cancer is present; they have many limitations (see the section, “The drawbacks of tumor markers”). Because of this, most doctors use only a few tumor markers. When a doctor looks at the level of a tumor marker, he or she will consider it along with the patient’s medical history, physical exam, and other lab tests or imaging tests.

Recently, doctors have begun to develop newer types of tumor markers. With advances in technology, levels of certain genetic materials (DNA or RNA) can now be measured. It’s been hard to identify single substances that provide useful information, but doctors are now beginning to look at patterns of genes or proteins in the blood. These new fields of genomics and proteomics are discussed in the section called “What’s new in tumor marker research?

Last Medical Review: 10/30/2013
Last Revised: 10/30/2013