Mammography (ma-MAH-gruh-fee) is a screening tool that uses X-rays to create an image of the breast. These images, called mammograms (MAM-o-grams), are used to find early signs of breast cancer such as a dense mass or clusters of calcium (microcalcifications).
Mammography is the best screening tool used today to find breast cancer. It can find cancers at an early stage, when they are small (too small to be felt) and most responsive to treatment.
Learn about mammography recommendations for women at average risk of breast cancer.
Learn about mammography recommendations for women at higher risk of breast cancer.
Where to get a mammogram
Mammograms can be done in:
- Certified radiology and imaging centers
- Mammography clinics
- Hospital radiology departments
- Mobile vans
- Some physicians’ offices
What to expect
Before the procedure, you will undress from the waist up, so it is a good idea to wear a shirt you can remove easily. Avoid using deodorants, antiperspirants, perfumes, powders or lotions in the breast and underarm area on the day of the exam. Ingredients in these products can show up on a mammogram and make it harder to interpret.
Getting a screening mammogram takes about 15 minutes. During the procedure, each breast is pressed between two plates, and an X-ray image is made. Two views of each breast are taken, one with the X-ray beam aimed from top to bottom and the other from side to side.
Sometimes, the pressure can be uncomfortable, but it usually only lasts a few seconds. Tell the mammography technologist if you feel any discomfort. Taking acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) about an hour before the exam may help. If you have concerns, talk to your health care provider about other ways to help ease discomfort (or anxiety) during a mammogram. And, before the exam, let your technologist know your concerns.
Standard (film) mammography versus digital mammography
X-ray images of the breast can be captured on film (standard mammography) or stored directly onto a computer (digital mammography). Film and digital mammography are similar in their ability to detect cancer [1-3].
Because digital images are viewed on a computer, they can be lightened or darkened, and certain sections can be enlarged and examined more closely. The ability to control the images on a computer makes digital mammography more accurate than standard film mammography for some women. And, because the images are stored on a computer, they can be shared more easily with another radiologist for review.
The Digital Mammographic Imaging Screening Trial compared film and digital mammography and found digital mammography was better at detecting cancer in [3]:
- Women who are premenopausal or peri-menopausal
- Women who are under age 50
- Women who have dense breast tissue
For women who do not fall in one of the above groups, digital mammography does not appear to offer benefit over standard film mammography.
Although digital mammography has become more common, it is not available at all centers.
If your insurance covers the cost of screening mammography, it should cover either type of mammography, standard film or digital. However, it is best to check with your insurance provider before having a digital mammogram to ensure the cost is covered.
Learn about low-cost or free mammograms.
Computer-assisted detection (CAD)
A radiologist trained to read mammograms, will examine your images for signs of breast cancer. Computer-assisted detection (CAD) software was developed to help radiologists find suspicious areas on a digital mammogram (or a standard mammogram converted to a digital image). CAD software analyzes the images and highlights potential areas of concern that should be examined more closely. It is commonly used to analyze mammograms in the United States.
Some studies suggest CAD may improve breast cancer detection [4-5]. However, the largest study to date showed CAD reduced the accuracy of the interpretation of mammograms compared to regular visual reading [6]. The authors found CAD actually led to an increase in false-positive results [6]. Thus, the benefit of CAD needs further study.
Learn more about false-positive results on screening tests.
Findings on a mammogram
Mammogram images appear in shades of black, gray and white, depending on the density of the tissue. Very dense tissue, like bone, shows up as white on an X-ray. Fat looks dark gray on an X-ray. Cancerous tumors and some benign breast conditions are denser than fat and appear a lighter shade of gray or white on an X-ray image.
Dense breast tissue
Dense breast tissue can look white or light gray on a mammogram. This can make mammograms harder to interpret in younger women, who tend to have denser breasts. After menopause, breast density decreases, making it easier to read the mammograms of postmenopausal women.
Some younger women may have lower breast density after an oophorectomy (removal of the ovaries) or hysterectomy (removal of the uterus). Older women who use postmenopausal hormones often have higher breast density until they stop using hormones.
For women with dense breast tissue, digital mammography is more accurate than standard mammography.
Learn about breast density and breast cancer risk.
Benign breast conditions
Some common benign breast conditions, such as cysts and fibroadenomas, may show up on mammograms as round or oval patches with distinct borders.
Learn more about benign breast conditions.
Calcifications and microcalcifications
Calcifications are bits of calcium that can show up on mammograms as small, bright white spots. Most calcifications are benign. However, certain patterns of calcifications are suspicious and need more testing. Tight clusters or lines of tiny calcifications (microcalcifications) can be a sign of cancer.
Calcifications are common and appear on about half of all mammograms in women ages 50 and older (and on about one in 10 mammograms of younger women) [7]. They may be related to older age, past injury to the breast or inflammation (swelling) of the breast tissue (from an infection, for example) [7].
Ductal carcinoma in situ (DCIS, non-invasive breast cancer)
Ductal carcinoma in situ (DCIS) is a non-invasive breast cancer. On a mammogram, DCIS usually looks like a cluster of microcalcifications. It can be difficult to know from a mammogram image whether the cluster is DCIS or invasive breast cancer.
Learn about follow-up after an abnormal mammogram.
Learn more about DCIS.
Invasive breast cancer
Invasive breast cancer cells do not stay within the clear borders that separate the cells from surrounding tissue. Instead, they invade the surrounding tissue. When this occurs, the core cancer cells appear as a light patch on a mammogram. The cells that have spread into the surrounding breast tissue have a fuzzy or spiky appearance (called spiculated) along their outer edge.
Learn about follow-up after an abnormal mammogram.
Recall rates
If a finding is abnormal, or the mammography image was not clear enough to read the results, you will be called back for a follow-up visit. Follow up may include another mammogram or an ultrasound. In some cases, a biopsy may be needed.
The recall rate of a mammography center is the percent of women who are called back for further tests. Some centers may share their recall rate with you and this information may help you understand your chances of being called back. It is not uncommon to be called back for an abnormal finding. Although there is no “gold standard” recall rate, on average, 10 percent of women are called back [8].
If you are called back, don’t panic. Most abnormal findings are not breast cancer.
Learn about follow-up after an abnormal mammogram.
Mammography results
Breast Imaging Reporting and Data System
Most mammography centers report the results of mammograms using the Breast Imaging Reporting and Data System (BI-RADS®). BI-RADS® was developed by the American College of Radiology to provide a standard way to describe the findings on mammograms (with categories numbered 0 to 6).
Learn more about the BI-RADS® categories for mammography findings.
When to expect mammography results
Some centers may give you the results of your mammogram at the time of your screening. However, depending on the center, it may take up to two weeks to get your results.
If you do not get your results within two weeks, follow up with your health care provider or the mammography center. Don’t assume the results were normal because you haven’t gotten a report.
Breast implants and mammography
Mammography is a safe and effective screening tool for women who have breast implants. However, if you have implants, it is important to tell your mammography technologist before the procedure. Special adjustment of the mammography machine is required to avoid too much pressure on the implant. Special positioning of the breast will also be required. Four views of each breast will be taken (instead of the standard two).
If possible, choose a center with technologists and radiologists who are experienced in mammography for women with breast implants.
Breastfeeding and mammography
While you are breastfeeding, the tissue in your breasts may appear dense on a mammogram, making it hard to read. So, it is best to wait until you stop breastfeeding to get a routine screening mammogram. However, you should discuss the best timing of your mammogram with your health care provider if you are due for screening.
If you have any concerns about your breasts (such as finding a lump or noting any change), see your provider.
Physical disabilities and breast cancer screening
Some women with physical disabilities have trouble finding a mammography center that meets their needs. Partnering with a health care provider can help things go more smoothly and may help increase access for other women.
Learn more about women with physical disabilities and breast cancer screening.
Radiation exposure during mammography
A woman is exposed to a small amount of radiation during a mammogram. While the radiation exposure during mammography can increase the risk of breast cancer over time, this increase in risk is very small [9-10]. Studies show the benefits of mammography outweigh the risks from radiation exposure especially for women ages 50 and older [9-11].
Although a recent media report suggested radiation during a mammogram might increase the risk of thyroid cancer, there is no scientific research to support this claim. Read the statement from the American College of Radiology and the Society of Breast Imaging addressing concerns about this false claim.
Low-cost or free mammography
Most insurance companies and Medicare cover the cost of mammograms. And, in many parts of the U.S., low-cost or free mammograms are offered through national programs and community organizations.
- Komen Affiliates fund breast cancer education, screening and treatment projects for those who need it most. Find an Affiliate in your area to learn what resources are available. Or, call our breast care helpline at 1-877 GO KOMEN (1-877-465-6636) to help find low-cost options in your area.
- National Breast and Cervical Cancer Control Program provides access to breast cancer screening to low-income, uninsured and underinsured women.
- YWCA provides breast cancer education and screening to women who lack access to health services.
Each October, during Breast Cancer Awareness Month, many imaging centers offer mammograms at reduced rates. For a list of certified centers, visit the FDA website (http://www.fda.gov/cdrh/mammography/certified.html).
Screening mammography trends
After mammography was shown to be an effective breast cancer screening tool in the late 1980's, the use of screening mammography in the U.S. quickly increased. In 1987, 29 percent of women 40 years and older reported having a mammogram within the past two years [12]. By 1990, use increased to 52 percent and by 2000, 70 percent of women 40 years and older reported having a recent mammogram [12].
In 2008, 67 percent of women 40 years and older (68 percent of white and African American women and 62 percent of Hispanic/Latino women) reported having a recent mammogram [12-13]. This was a slight decline from 2000 [12-14]. The cause(s) for this decline are not yet known [13-14]. There is concern this decrease in screening mammography may lead to an increase in breast cancer mortality because fewer cancers will be found early, when they are most treatable.
Learn more about race and ethnicity issues in screening.
Updated 01/24/12
