Breast Cancer Prevention and Early Detection

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A mammogram is an x-ray of the breast. A diagnostic mammogram is used to diagnose breast disease in women who have breast symptoms or an abnormal result on a screening mammogram. Screening mammograms are used to look for breast disease in women who are asymptomatic; that is, those who appear to have no breast problems. Standard screening mammograms take 2 views (x-ray pictures taken from different angles) of each breast. Women who are breastfeeding can still get mammograms, although these are probably not quite as accurate because the breast tissue tends to be dense.

For a mammogram, the breast is compressed between 2 plates for a few seconds to flatten and spread the tissue. This may be uncomfortable for a moment, but it is necessary to produce a good, readable mammogram.

The procedure produces a black and white image of the breast tissue either on a large sheet of film or as a digital computer image that is “read,” or interpreted, by a radiologist (a doctor trained to interpret images from x-rays, ultrasound, magnetic resonance imaging, and related tests.) If the image is recorded on the computer instead of on film, it is called a digital mammogram (also known as a full-field digital mammogram or FFDM). This is available at most centers.

A newer type of mammogram, called breast tomosynthesis or 3-D mammography is available. For this test, the breast is compressed once and a machine takes many low-dose x-ray images as it moves over the breast. The images are recorded on a computer, which can be combine them into a 3-dimensional picture. 3-D mammography uses more radiation than most standard 2-view mammograms, but it may let doctors see problem areas more clearly. This might lower the chance that you will need to be called back for another mammogram right away. It may also be able to find more cancers.

Limitations of mammograms

A mammogram cannot prove that an abnormal area is cancer. To confirm whether cancer is present, a small amount of tissue must be removed and looked at under a microscope. This procedure is called a biopsy. For more information, see our document For Women Facing a Breast Biopsy.

You should also be aware that mammograms are done to find cancers that can’t be felt. If you have a breast lump, you should have it checked by your doctor, who may recommend a biopsy even if your mammogram result is normal. Mammograms are not perfect at finding breast cancer. They do not work as well in women with dense breasts, since dense breasts can hide a tumor. Dense breasts are more common in younger women, pregnant women, and women who are breastfeeding, but any woman can have dense breasts.

This can be a problem for younger women who need breast screening because they are at high risk for breast cancer (because of gene mutations, a strong family history of breast cancer, or other factors). This is one of the reasons that the American Cancer Society recommends MRI scans in addition to mammograms for screening in these women.

At this time, American Cancer Society guidelines do not contain recommendations for additional testing to screen women with dense breasts who aren’t at high risk of breast cancer based on other risk factors.

For more information on mammograms and other imaging tests for early detection and diagnosis of breast diseases, see our document Mammograms and Other Breast Imaging Procedures.

Last Medical Review: 09/10/2014
Last Revised: 08/19/2015