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Reviewed by: Emily F. Conant, MD

Updated October 1, 2010

Mammograms are tests used to screen for breast cancer and to diagnose and evaluate breast abnormalities.

If you have not had breast cancer, you should have a mammogram once each year after you turn age 40. If you are at high risk for developing breast cancer or you have a strong family history of the disease, you may begin mammograms earlier than age 40.

Mammograms are used for screening when a woman has no symptoms of breast cancer. They are also used to diagnose breast cancer, to learn more about an area of abnormality or after treatment to look at the response of a breast cancer to therapy.

Some testing centers provide film mammograms, which are black and white pictures of the breast recorded onto film. Others provide digital mammograms which record the images onto a computer, allowing the radiologist to change the contrast of the image and zoom in to look more carefully at different portions of the breast. This type of mammogram is more effective for younger women and women with dense breasts, but it is expensive and not all centers offer it.

Getting the Test

You will need to remove your shirt and bra, and you should not wear deodorant. During the test, your breasts will be compressed between two plates while a camera attached to the plates takes pictures of your breasts from different angles. If you have had surgery before, small metal balls or BBs will be taped to the scars on your skin to help the radiologist identify those areas. You will be exposed to a very small amount of radiation that is not harmful to you.

You may worry about pain while the plates compress your breasts and the camera takes pictures. Some people have some pain, but the pain goes away quickly most of the time after the test ends. If you are about to have your period and your breasts are tender, you may have more pain than you would at other times of the month.

After the test, your radiologist may read the results right away, or the mammogram may be sent away for evaluation. If an abnormality is present or if the films are not clear, you could be called back for an another mammogram or study.

The Results

You may fear having a mammogram because you feel anxious about the results. Do not be alarmed if your test shows an area that needs extra imaging. About 10 percent of women who have mammograms need more imaging, but often the area seen on the mammogram does not turn out to abnormal.

A mammogram could find a number of different breast changes, of which many are not cancer. Your radiologist will look for asymmetric areas, areas where breast density is inconsistent, breast masses, thickening of the skin or calcifications (tiny specks of calcium about the size of sand grains, which are usually harmless but could be a sign of cancer). A mammogram can find many changes that actually turn out to be benign (not cancer), such as fluid-filled pockets called cysts, or solid, round masses called fibroadenomas.

Unfortunately, sometimes a biopsy is needed to make sure that the changes seen on a mammogram really are benign. Also, mammograms do not always reveal cancers when they are present. Sometimes other testing is needed if your radiologist continues to see something of concern in your breast.