Tumor markers are substances that can be found in the system, normally in the blood or urine, when the cancer is present. They can be used together with other tests to help diagnosing the type of cancer and monitoring the treatment, in some cases. At their most, they are proteins or piece of proteins, including cell surface antigens, cytoplasmic proteins, enzymes and hormones.
There are a lot of tumor markers. Some are connected to a sole type of cancer, while the others can be founded in several types. To verify the presence of a tumor marker, a patient’s blood or urine sample is sent to be analyzed at a pathology laboratory. Sometimes it is sent a sample of the tumor itself.
Rarely they are enough to identify if there is a cancer or not. Benign diseases, sometimes, can increase the level of certain markers. On the other hand, not all people with cancer can have those levels increased. When a doctor evaluates the result of a marker, he/she considers the patient history and the physical exam, as well as imaging and lab tests.
Unfortunately, a few tumor markers can detect cancer in the initial stages. Almost all people have a low amount of those markers in the blood, that is why it is so difficult to detect cancer using only those tests, and the level of those markers can increase when the disease is advanced. Some diagnosed patients never presented elevated levels of tumor markers. Even when the levels of those markers are high, it does not mean that there is a cancer. For instance, the level of tumor marker CA 125 can be elevated in women with another gynecological condition besides ovary cancer.