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A mammogram is a low-dose x-ray exam of the breasts to look for changes that are not normal. The results are recorded on x-ray film or directly into a computer for a doctor called a radiologist to examine.
A mammogram allows the doctor to have a closer look for changes in breast tissue that cannot be felt during a breast exam. It is used for women who have no breast complaints and for women who have breast symptoms, such as a change in the shape or size of a breast, a lump, nipple discharge, or pain. Breast changes occur in almost all women. In fact, most of these changes are not cancer and are called “benign,” but only a doctor can know for sure. Breast changes can also happen monthly, due to your menstrual period.
A high-quality mammogram plus a clinical breast exam, an exam done by your doctor, is the most effective way to detect breast cancer early. Finding breast cancer early greatly improves a woman's chances for successful treatment.
Like any test, mammograms have both benefits and limitations. For example, some cancers can't be found by a mammogram, but they may be found in a clinical breast exam.
Checking your own breasts for lumps or other changes is called a breast self-exam (BSE). Studies so far have not shown that BSE alone helps reduce the number of deaths from breast cancer. BSE should not take the place of routine clinical breast exams and mammograms.
If you choose to do BSE, remember that breast changes can occur because of pregnancy, aging, menopause, menstrual cycles, or from taking birth control pills or other hormones. It is normal for breasts to feel a little lumpy and uneven. Also, it is common for breasts to be swollen and tender right before or during a menstrual period. If you notice any unusual changes in your breasts, contact your doctor.
You stand in front of a special x-ray machine. The person who takes the x-rays, called a radiologic technician, places your breasts, one at a time, between an x-ray plate and a plastic plate. These plates are attached to the x-ray machine and compress the breasts to flatten them. This spreads the breast tissue out to obtain a clearer picture. You will feel pressure on your breast for a few seconds. It may cause you some discomfort; you might feel squeezed or pinched. This feeling only lasts for a few seconds, and the flatter your breast, the better the picture. Most often, two pictures are taken of each breast — one from the side and one from above. A screening mammogram takes about 20 minutes from start to finish.
A digital mammogram also uses x-rays to produce an image of the breast, but instead of storing the image directly on film, the image is stored directly on a computer. This allows the recorded image to be magnified for the doctor to take a closer look. Current research has not shown that digital images are better at showing cancer than x-ray film images in general. But, women with dense breasts who are pre- or perimenopausal, or who are younger than age 50, may benefit from having a digital rather than a film mammogram. Digital mammography may offer these benefits:
The United States Preventive Services Task Force (USPSTF) recommends:
The radiologist will look at your x-rays for breast changes that do not look normal and for differences in each breast. He or she will compare your past mammograms with your most recent one to check for changes. The doctor will also look for lumps and calcifications.
If calcifications are grouped together in a certain way, it may be a sign of cancer. Depending on how many calcium specks you have, how big they are, and what they look like, your doctor may suggest that you have other tests. Calcium in the diet does not create calcium deposits, or calcifications, in the breast.
If you have a screening test result that suggests cancer, your doctor must find out whether it is due to cancer or to some other cause. Your doctor may ask about your personal and family medical history. You may have a physical exam. Your doctor also may order some of these tests:
Women can get high-quality mammograms in breast clinics, hospital radiology departments, mobile vans, private radiology offices, and doctors’ offices. The Food and Drug Administration (FDA) certifies mammography facilities that meet strict quality standards for their x-ray machines and staff and are inspected every year. You can ask your doctor or the staff at the mammography center about FDA certification before making your appointment. A list of FDA-certified facilities can be found on the Internet.
Your doctor, local medical clinic, or local or state health department can tell you where to get no-cost or low-cost mammograms. You can also call the National Cancer Institute's Cancer Information Service toll free at 800-422-6237.
Women with breast implants should also have mammograms. A woman who had an implant after breast cancer surgery in which the entire breast was removed (mastectomy) should ask her doctor whether she needs a mammogram of the reconstructed breast.
If you have breast implants, be sure to tell your mammography facility that you have them when you make your appointment. The technician and radiologist must be experienced in x-raying patients with breast implants. Implants can hide some breast tissue, making it harder for the radiologist to see a problem when looking at your mammogram. To see as much breast tissue as possible, the x-ray technician will gently lift the breast tissue slightly away from the implant and take extra pictures of the breasts.
First, check with the place you are having the mammogram for any special instructions you may need to follow before you go. Here are some general guidelines to follow:
Although they are not perfect, mammograms are the best method to find breast changes that cannot be felt. If your mammogram shows a breast change, sometimes other tests are needed to better understand it. Even if the doctor sees something on the mammogram, it does not mean it is cancer.
As with any medical test, mammograms have limits. These limits include:
For more information about mammograms, call womenshealth.gov at 800-994-9662 (TDD: 888-220-5446) or contact the following organizations:
Mammograms fact sheet was reviewed by:
Worta McCaskill-Stevens, M.D.
Community Oncology and Prevention Trials Research Group
Division of Cancer Prevention
National Cancer Institute, National Institutes of Health
Richard E. Manrow, Ph.D.
Associate Director, Office of Cancer Content Management
Office of Communications and Education
National Cancer Institute, National Institutes of Health
Content last updated: June 21, 2013.
Resources last updated: September 25, 2013.