Test Overview

A mammogram is an X-ray test of the breasts (mammary glands) used to screen for breast problems, such as a lump, and whether a lump is fluid-filled (a cyst) or a solid mass.

A mammogram is done to help screen for or detect breast cancer. Many small tumors can be seen on a mammogram before they can be felt by a woman or her health professional. Cancer is most easily treated and cured when it is discovered in an early stage. Mammograms do not prevent breast cancer or reduce a woman's risk of developing cancer. But regular mammograms can reduce a woman's risk of dying from breast cancer by detecting a cancer when it is more easily treated.

Experts differ in their recommendations about when or how often women should have mammograms.

  • For women between the ages of 40 and 50, the benefits of regular mammograms are not clear. Women should discuss the benefits and harms of mammograms with their doctors. Talk with your doctor to decide when to start and how often to have a mammogram.
    • The U.S. Preventive Services Task Force (USPSTF) does not recommend routine mammograms for women ages 40 to 49. They say women should decide when to start having regular mammograms based on their situations, their individual risks, and what they prefer.
    • Some organizations recommend women have mammograms every 1 to 2 years, starting at age 40.
  • For women older than age 50, regular mammograms are recommended.
    • The USPSTF recommends routine mammograms every 2 years for women ages 50 to 74.
    • Some organizations recommend women have yearly mammograms for as long as they are in good health.
  • Women age 75 and older may want to talk to their doctors about whether they need breast cancer screening.

Your doctor may recommend testing at a younger age if you have risk factors for breast cancer.

A mammogram that appears to detect a cancer, when in fact a cancer is not present (false-positive results), can occur at any age but is more likely to occur in younger women. About 5% to 10% of screening mammograms will require more testing. This may include another mammogram of specific breast tissue (compression view) or another test, such as an ultrasound or biopsy. Most of these tests will show no cancer is present.

Why It Is Done

A mammogram is done to:

  • Screen for breast cancer in women without symptoms.
  • Detect breast cancer in women with symptoms. Symptoms of breast cancer may include a lump or thickening in the breast, nipple discharge, or dimpling of the skin on one area of the breast.
  • Locate an area of suspicious breast tissue to remove for examination under a microscope (biopsy) when an abnormality is found.

How To Prepare

If you have previously had a mammogram done at another clinic, have the results sent or bring them with you to your examination.

Tell your health professional if you:

  • Are or might be pregnant. A mammogram is an X-ray test with exposure to low-dose radiation and is not done for routine screening during pregnancy.
  • Are breast-feeding. A mammogram may not provide clear results in breasts that contain milk.
  • Have breast implants. Breast implants require a modified mammogram method.
  • Have previously had a breast biopsy. Knowing the location of scar tissue will help the radiologist read your mammogram accurately.

On the day of the mammogram, do not use any deodorant, perfume, powders, or ointments on your breasts. The residue left on your skin by these substances may interfere with the X-rays.

If you are still having menstrual periods, you may want to have your mammogram done within 2 weeks after your menstrual period ends. The procedure will be more comfortable, especially if your breasts become tender before your period starts.

How It Is Done

A mammogram is done by a radiology technologist or mammogram technologist. The X-ray pictures (mammograms) are interpreted by a doctor who specializes in evaluating X-rays (radiologist).

You will need to remove any jewelry that might interfere with the X-ray picture. You will need to take off your clothes above the waist, and you will be given a cloth or paper gown to use during the test. If you are concerned about an area of your breast, show the technologist so that the area can be noted.

You usually stand during a mammogram; sometimes you may also be asked sit or lie down, depending upon the type of X-ray equipment used. One at a time, your breasts will be placed on a flat plate that contains the X-ray film. Another plate is then pressed firmly against your breast to help flatten out the breast tissue. Very firm compression is needed to obtain high-quality pictures. You may be asked to lift your arm or use your hand to hold your other breast out of the way. For a few seconds while the X-ray picture is being taken, you will need to hold your breath. Usually at least two pictures are taken of each breast: one from the top and one from the side.

You may be in the mammogram clinic for up to an hour; the mammogram itself takes about 10 to 15 minutes. You will be asked to wait (usually about 5 minutes) until the X-rays are developed, in case repeat pictures need to be taken. In some clinics and hospitals, X-ray pictures can be viewed immediately on a computer screen (digitally).

How It Feels

A mammogram is often uncomfortable but rarely extremely painful. If you have sensitive or fragile skin, or a skin condition, let the technician know before you have your exam. If you have menstrual periods, the procedure is more comfortable when done within 2 weeks after your period has ended.

The X-ray plate will feel cold when you place your breast on it. Having your breasts flattened and squeezed is usually uncomfortable. But it is necessary to flatten out the breast tissue to obtain the best pictures.


A mammogram may appear to detect a cancer even when a cancer is not present (false-positive results). This can occur at any age but is more likely with younger women. False-positive results can lead to emotional distress and unneeded tests and treatments.

Also, a mammogram may detect abnormalities that will not develop into life-threatening cancer. Tests and treatment after this kind of discovery are not needed and can be harmful.

There is always a slight risk of damage to cells or tissue from being exposed to any radiation, including the very low levels of radiation used for this test. But the risk of damage from the X-rays is very low compared with the potential benefits of the test.


A mammogram is an X-ray test of the breasts (mammary glands) that is used to screen for breast problems, such as a lump, and whether a lump is fluid-filled (a cyst) or a solid mass. Mammogram results are usually available within 10 days. It is not uncommon to be asked to return for another test so an additional view of an area in question can be obtained.

In the United States, facilities that perform mammograms send the results directly to your health professional's office and must send you a copy of the test results (written in language that is easily understood) within 30 days.



Breast tissue looks normal. No unusual growths, lumps, or other types of abnormal tissue are seen. The glands that produce milk for breast-feeding and the tubes (ducts) through which milk flows appear normal.


An abnormal growth, lump, or other type of tissue may be seen. A cancerous (malignant) or noncancerous (benign) tumor may be seen. One or more fluid-filled pockets (cysts) may be seen.

Bits of calcium (calcifications) may be seen. Tiny calcifications (microcalcifications) often occur in areas where cells are growing very rapidly (such as in a cancerous tumor). Larger calcifications (macrocalcifications) are usually normal and noncancerous in women over the age of 50.

Need more information:

A specific area needs to be looked at again. This is a very common result for many women and does not mean that the area is abnormal or cancerous.

Most abnormalities found during a mammogram are not breast cancer. But many women who have regular screening mammograms need additional tests to investigate any abnormalities found during a mammogram. If an area of your breast tissue appears to be a concern during a mammogram, other tests may be done.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Deodorant, perfume, powders, or ointments applied to the breasts or under the arms before the test. They may interfere with the X-ray pictures.
  • Breast implants or scar tissue from previous breast surgery. This may make a mammogram more difficult to interpret.

A mammogram is not usually done if you are:

  • Pregnant, because the radiation could damage your developing baby (fetus). If a mammogram is absolutely necessary for diagnosing a problem, a lead apron will be placed over your abdomen to shield your baby from exposure to the X-rays.
  • Breast-feeding, because breasts that contain milk are very difficult to examine.

What To Think About

  • Most abnormalities found during a mammogram are not breast cancer. But many women who have regular screening mammograms need additional tests to investigate any abnormalities found during a mammogram. If an area of your breast tissue appears to be a concern during a mammogram, other tests may be done.
    • A compression view mammogram, which is similar to a regular mammogram, is usually done to get a better view of specific breast tissue.
    • Breast ultrasound, which produces images of the breast from sound waves, may be done if a lump is found during a clinical breast examination or on a mammogram. Ultrasound can help determine whether a breast lump is a fluid-filled cyst or a solid tumor. For more information, see the medical test Breast Ultrasound.
    • Breast biopsy may be done if a lump is found in the breast. For a biopsy, the lump or a piece of the lump is removed and examined under a microscope to determine whether cancer cells are present. For more information, see the medical test Breast Biopsy.
  • A normal mammogram does not guarantee that breast cancer is not present.
  • Mammogram results are more difficult to interpret in women before menopause because breast tissue in younger women is denser than in older women. Mammograms may be less accurate in obese women.
  • A mammogram is currently the most accurate test for detecting breast cancer. But other tests, such as magnetic resonance image (MRI) and nuclear scan tests, can also be done to detect breast cancer.
    • MRI can detect suspicious areas in the breasts, but many suspicious areas turn out to be normal (false-positive results). MRI is useful when a diagnosis is difficult to make using other methods. An MRI can also detect if a breast implant has ruptured. MRI is much more expensive and less widely available than a mammogram. It is not used very often to examine the breasts.
    • Nuclear scan tests use a radioactive tracer (called a radionuclide) that is injected into a vein. The tracer travels through the blood vessels and can accumulate in many types of tumors. The location of the tracer is detected by a camera that scans the body for areas where the tracer has accumulated. Nuclear scanning tests are useful when a diagnosis is difficult to make using other methods.
  • A new mammogram technique called digital mammogram allows your health professional to view different parts of the breast without taking additional images. Digital mammograms have the same overall accuracy as standard mammograms, but they are more accurate for screening women under age 50 and for women with very dense breast tissue.1 The procedure in which a digital mammogram is done is the same as a standard mammogram; each procedure takes about the same amount of time and breast compression is needed for both. Images from digital mammogram can be magnified and stored electronically more easily than images from a standard mammogram. Digital mammograms are not available at all centers.
  • In the United States, facilities that perform mammograms must give a woman her original mammogram pictures (not copies) if she requests them.
  • If you come from a family where women have had breast cancer earlier than age 40, talk to your doctor about what age to start screening. If you have a very strong family history of breast or ovarian cancer, you may want to have a breast cancer (BRCA) gene test. For more information, see the medical test Breast Cancer (BRCA) Gene Test.



  1. Pisano ED, et al. (2005). Diagnostic performance of digital versus film mammography for breast-cancer screening. New England Journal of Medicine, 353(17): 1773–1783

Other Works Consulted

  • American Cancer Society (2009). Prevention and Early Detection: American Cancer Society Guidelines for the Early Detection of Cancer. Atlanta: American Cancer Society. Available online:
  • U.S. Preventive Services Task Force (2009). Screening for breast cancer. Available online:


Author Sandy Jocoy, RN
Editor Maria Essig
Associate Editor Tracy Landauer
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer Deborah A. Penava, BA, MD, FRCSC, MPH - Obstetrics and Gynecology
Last Updated February 12, 2009

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