Tests are used to screen for different types of cancer.

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, the chance of recovery is better if the disease is found and treated at an early stage.

Clinical trials that study cancer screening methods are taking place in many parts of the country. Information about ongoing clinical trials is available from the NCI Web site.

Three tests are commonly used to screen for breast cancer:

Mammogram

A mammogram is an x-ray of the breast. This test may find tumors that are too small to feel. A mammogram may also find ductal carcinoma in situ, abnormal cells in the lining of a breast duct, which may become invasive cancer in some women. The ability of a mammogram to find breast cancer may depend on the size of the tumor, the density of the breast tissue, and the skill of the radiologist.

Mammography of the right breast.

Clinical breast exam (CBE)

A clinical breast exam is an exam of the breast by a doctor or other health professional. The doctor will carefully feel the breasts and under the arms for lumps or anything else that seems unusual.

Breast self-exam (BSE)

Breast self-exam is an exam to check your own breasts for lumps or anything else that seems unusual.

If a lump or other abnormality is found using one of these 3 tests, ultrasound may be used to learn more. It is not used by itself as a screening test for breast cancer. Ultrasound is a procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram.

New screening tests are being studied in clinical trials.

MRI (magnetic resonance imaging)

MRI is a procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI). MRI does not use any x-rays.

In women with a high inherited risk of breast cancer, screening trials of MRI breast scans have shown that MRI is more sensitive than mammography for finding breast tumors. It is common for MRI breast scan results to appear abnormal even though no cancer is present. Screening studies of breast MRI in women at high inherited risk are ongoing.