There are several types of mammograms. They include:
- Standard mammogram, which puts images of the breast on film.
- Digital mammogram, which puts images of the breast into an electronic file. This allows your doctor to see different views of the breast without taking more images.
Digital breast tomosynthesis is sometimes called 3-D mammogram. It uses X-rays to create a three-dimensional image of the breast. This is a newer test that may be used alone or with a digital mammogram.
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 for women ages 40 to 74, mammograms may help reduce deaths from breast cancer.footnote 1
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 or another test, such as an ultrasound. Most of these tests will show no cancer is present.
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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 doctor 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 breastfeeding. 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.
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 jewellery 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.
For a standard or digital mammogram, you usually stand during the test. One at a time, your breasts will be placed on a flat plate. 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. 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.
For a 3-D mammogram, you will also stand, and your breast will be positioned on a flat plate. The top plate is pressed against your breast with just enough pressure to keep the breast in position while the X-ray tube moves around the breast. Many images are taken in a very short time. A computer is used to combine these images to create a three-dimensional picture of the breast.
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 examination. 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 help find cancer early. But finding cancer early doesn't always save lives. In some cases the cancer will have already spread to other parts of the body.
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.
A mammogram may miss finding breast cancer even when it is there (false-negative results). This is more likely to happen with young women who have dense breasts. False-negative results can keep a woman from getting treatment and can give her a false sense of security.
Also, mammograms may find certain types of breast cancer that would never cause symptoms or threaten a woman's life. But doctors cannot tell what kinds of cancer will cause problems, so all cancers are treated. This means that women may end up having tests and treatments they don't need. These can cause harm.
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 of the breast that is used to screen for breast cancer. 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.
The results of a screening mammogram are sent directly to your family doctor's office. And in some provinces, they also will be sent directly to you. If the mammogram is done to diagnose a problem, the results will be sent to your family doctor, and he or she will discuss the results with you. If you have a mammogram that was not ordered by your doctor, a copy of the results will be sent to you.
Breast tissue looks normal. No unusual growths, lumps, or other types of abnormal tissue are seen. The glands that produce milk for breastfeeding 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 non-cancerous (benign) tumour 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 tumour). Larger calcifications (macrocalcifications) are usually normal and non-cancerous in women older than age 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 more 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 harder 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 needed for diagnosing a problem, a lead apron will be placed over your abdomen to shield your baby from exposure to the X-rays.
- Breastfeeding, 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 more 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 such as an ultrasound may be done.
- Mammogram results are harder 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.
- Digital mammograms have the same overall accuracy as standard mammograms. Researchers think that 3-D mammograms might make it easier to see breast cancer in women who have dense breasts.
- 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 genetic testing.
- Canadian Task Force on Preventive Health Care (2018). Recommendations on screening for breast cancer in women aged 40–74 years who are not at increased risk for breast cancer. CMAJ, 190(49): E1441–E1451. DOI: 10.1503/cmaj.180463. Accessed December 20, 2018.
Other Works Consulted
- American Cancer Society (2012). American Cancer Society Guidelines for the Early Detection of Cancer. Atlanta: American Cancer Society. Available online: http://www.cancer.org/Healthy/FindCancerEarly/CancerScreeningGuidelines/american-cancer-society-guidelines-for-the-early-detection-of-cancer.
- American College of Obstetricians and Gynecologists (2011). Breast cancer screening. ACOG Practice Bulletin No. 122. Obstetrics and Gynecology, 118: 372–382.
- U.S. Preventive Services Task Force (2009). Screening for breast cancer. Available online: http://www.uspreventiveservicestaskforce.org/uspstf/uspsbrca.htm.
Current as of: August 22, 2019
Author: Healthwise Staff
Kathleen Romito MD - Family Medicine
Brian D. O'Brien MD - Internal Medicine
Kirtly Jones MD - Obstetrics and Gynecology
Current as of: August 22, 2019