Medically reviewed on March 22, 2018
A mammogram is an X-ray image of your breasts used to screen for breast cancer. Mammograms play a key role in early breast cancer detection and help decrease breast cancer deaths.
During a mammogram, your breasts are compressed between two firm surfaces to spread out the breast tissue. Then an X-ray captures black-and-white images of your breasts that are displayed on a computer screen and examined by a doctor who looks for signs of cancer.
A mammogram can be used either for screening or for diagnostic purposes. How often you should have a mammogram depends on your age and your risk of breast cancer.
During a mammogram, you stand in front of an X-ray machine designed for mammography. A technician places your breast on a platform that holds the X-ray film and positions the platform to match your height. The technician helps you position your head, arms and torso to allow an unobstructed view of your breast.
Why it's done
Mammography is X-ray imaging of your breasts designed to detect tumors and other abnormalities. Mammography can be used either for screening or for diagnostic purposes in evaluating a breast lump:
- Screening mammography. Screening mammography is used to detect breast changes in women who have no signs or symptoms or new breast abnormalities. The goal is to detect cancer before clinical signs are noticeable.
- Diagnostic mammography. Diagnostic mammography is used to investigate suspicious breast changes, such as a new breast lump, breast pain, an unusual skin appearance, nipple thickening or nipple discharge. It's also used to evaluate abnormal findings on a screening mammogram. A diagnostic mammogram includes additional mammogram images.
When to begin screening mammography
There is no ideal age to start screening for breast cancer. Further, experts and medical organizations don't agree on when women should begin regular mammograms or how often the tests should be performed. Talk with your doctor about your risk factors, your preferences, and the benefits and risks of screening. Together, you can decide what screening mammography schedule is best for you.
Some general guidelines for when to begin screening mammography include:
- Women with an average risk of breast cancer. Many women begin mammograms at age 40 and have them every one to two years. Professional groups differ on their recommendations. The American Cancer Society advises women with an average risk to begin screening mammograms yearly at age 45 until age 54, and then continue every two years for at least the next 10 years. The U.S. Preventive Services Task Force recommends women start screening every two years starting at age 50 until age 74. However, these groups agree that women can choose to be screened starting at age 40.
- Women with a high risk of breast cancer. Women with a high risk of breast cancer may benefit by beginning screening mammograms before age 40. Talk to your doctor about evaluating your individual risk of breast cancer. Your risk factors, such as a family history of breast cancer or a history of precancerous breast lesions, may lead your doctor to recommend magnetic resonance imaging (MRI) in combination with mammograms.
Risks and limitations of mammograms include:
- Mammograms expose you to low-dose radiation. The dose is very low, though, and for most women the benefits of regular mammograms outweigh the risks posed by this amount of radiation.
- Mammograms aren't always accurate. The accuracy of the procedure depends in part on the technique used and the experience and skill of the radiologist. Other factors — such as your age and breast density — may result in false-negative or false-positive mammograms.
- Mammograms in younger women can be difficult to interpret. The breasts of younger women contain more glands and ligaments than do those of older women, resulting in dense breast tissue that can obscure signs of cancer. With age, breast tissue becomes fattier and has fewer glands, making it easier to interpret and detect changes on mammograms.
Having a mammogram may lead to additional testing. Among women of all ages, about 10 percent of mammograms require additional testing, including additional imaging tests such as ultrasound, and a procedure (biopsy) to remove a sample of breast tissue for laboratory testing. However, most abnormal findings detected on mammograms aren't cancer.
If you're told that your mammogram is abnormal, your radiologist will want to compare it with previous mammograms. If you have had mammograms performed elsewhere, your radiologist will ask for your permission to have them sent to the radiology center so that they can be compared with the current mammogram.
- Screening mammography can't detect all cancers. Some cancers detected by physical examination may not be seen on the mammogram. A cancer may be too small or may be in an area that is difficult to view by mammography, such as your armpit. Mammograms can miss 1 in 5 cancers in women.
- Not all of the tumors found by mammography can be cured. Certain types of cancers are aggressive, grow rapidly and spread early to other parts of your body.
How you prepare
To prepare for your mammogram:
- Choose a certified mammogram facility. Ask whether the mammogram facility is certified by the Food and Drug Administration. This certification will ensure that the facility meets certain standards.
- Schedule the test for a time when your breasts are least likely to be tender. If you haven't gone through menopause, that's usually during the week after your menstrual period. Your breasts are most likely to be tender the week before and the week during your period.
- Bring your prior mammogram images. If you're going to a new facility for your mammogram, request to have any prior mammograms placed on a CD. Bring the CD with you to your appointment so that the radiologist can compare past mammograms with your new images.
- Don't use deodorant before your mammogram. Avoid using deodorants, antiperspirants, powders, lotions, creams or perfumes under your arms or on your breasts. Metallic particles in powders and deodorants could be visible on your mammogram and cause confusion.
- Consider an over-the-counter pain medication if you find that having a mammogram is uncomfortable. Taking an over-the-counter pain medication, such as aspirin, acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others), about an hour before your mammogram might ease the discomfort of the test.
What you can expect
During the test
At the testing facility, you're given a gown and asked to remove neck jewelry and clothing from the waist up. To make this easier, wear a two-piece outfit that day.
For the procedure itself, you stand in front of an X-ray machine specially designed for mammography. The technician places one of your breasts on a platform and raises or lowers the platform to match your height. The technician helps you position your head, arms and torso to allow an unobstructed view of your breast.
Your breast is gradually pressed against the platform by a clear plastic plate. Pressure is applied for a few seconds to spread out the breast tissue. The pressure isn't harmful, but you may find it uncomfortable or even painful. If you have too much discomfort, tell the technician.
Your breast must be compressed to even out its thickness and permit the X-rays to penetrate the breast tissue. The pressure also holds your breast still to decrease blurring from movement and minimizes the dose of radiation needed. During the brief X-ray exposure, you'll be asked to stand still and hold your breath.
After the test
After images are made of both your breasts, you may be asked to wait while the technician checks the quality of the images. If the views are inadequate for technical reasons, you may have to repeat part of the test. The entire procedure usually takes less than 30 minutes. Afterward, you may dress and resume normal activity.
In the United States, federal law requires mammogram facilities to send your results within 30 days, but you can usually expect to receive your results sooner. Ask the technician what you can expect.
In addition, many states have passed legislation requiring mammogram facilities to inform you about the density of your breast tissue on the mammogram.
Mammography produces mammograms — black-and-white images of your breast tissue. Mammograms are digital images that appear on a computer screen. A radiologist interprets the images and sends a written report of the findings to your doctor.
The radiologist looks for evidence of cancer or noncancerous (benign) conditions that may require further testing, follow-up or treatment.
Possible findings include:
- Calcium deposits (calcifications) in ducts and other tissues
- Masses or lumps
- Asymmetric areas on the mammogram
- Dense areas appearing in only one breast or one specific area on the mammogram
- New dense area that has appeared since your last mammogram
Calcifications can be the result of cell secretions, cell debris, inflammation and trauma, among other causes. Tiny, irregular deposits called microcalcifications may be associated with cancer. Larger, coarser areas of calcification may be caused by aging or by a benign condition such as fibroadenoma, a common noncancerous tumor of the breast. Most breast calcifications are benign, but if calcifications are irregular in appearance, have increased in number or appear worrisome, the radiologist might order additional diagnostic images with magnification.
Dense areas indicate tissue that is more glandular than fatty, which can make calcifications and masses more difficult to identify or differentiate from normal glandular tissue. Dense areas can also represent cancer. Distorted areas suggest tumors that may have invaded neighboring tissues.
If the radiologist notes areas of concern on your mammogram, further testing may include additional mammograms, known as compression or magnification views, as well as ultrasound imaging or a procedure (biopsy) to remove a sample of breast tissue for laboratory testing. Some situations require the use of diagnostic magnetic resonance imaging (MRI) in areas where the current imaging with mammography or ultrasound is negative and it's not clear what's causing a breast change or abnormality.
Calcifications are small calcium deposits in the breast that show up as white spots on a mammogram. Large, round or well-defined calcifications (shown left) are more likely to be noncancerous (benign). Tight clusters of tiny, irregularly shaped calcifications (shown right) may indicate cancer.