Some screening tests are used because they have been shown to be helpful both in finding cancers early and in decreasing the chance of dying from these cancers. Other tests are used because they have been shown to find cancer in some people; however, it has not been proven in clinical trials that use of these tests will decrease the risk of dying from cancer.

Scientists study screening tests to find those with the fewest risks and most benefits. Cancer screening trials also are meant to show whether early detection (finding cancer before it causes symptoms) decreases a person's chance of dying from the disease. For some types of cancer, finding and treating the disease at an early stage may result in a better chance of recovery.

Clinical trials that study cancer screening methods are taking place in many parts of the country.

Skin examinations are commonly used to screen for melanoma.

Regular examination of the skin by both you and your doctor increases the chance of finding melanoma early. Most melanomas that appear in the skin can be seen by the naked eye. Usually, there is a long period of time when the tumor grows beneath the top layer of skin but does not grow into the deeper skin layers. This period of slow growth allows time for skin cancer to be found early. Skin cancer may be cured if the tumor is found before it spreads deeper. Monthly self-examination of the skin may help find changes that should be reported to a doctor. Regular skin checks by a doctor are important for people who have already had skin cancer.

If an area on the skin looks abnormal, a biopsy is usually done. The doctor will remove as much of the suspicious tissue as possible with a local excision. A pathologist then looks at the tissue under a microscope to check for cancer cells. Because it is sometimes difficult to tell if a skin growth is benign (not cancer) or malignant (cancer), you may want to have the biopsy sample checked by a second pathologist.

Other screening tests are being studied in clinical trials.