Breast density is a measure used to describe mammogram images. It’s not a measure of how the breasts feel.
Breasts are made up of breast tissue (the milk ducts and lobules, which may be called glandular tissue) and fat. Connective tissue helps hold everything place. Learn more about breast anatomy.
Breast density compares the area of breast and connective tissue seen on a mammogram to the area of fat. Breast and connective tissue are denser than fat and this difference shows up on a mammogram (see images below).
By looking at your mammogram or the measure of breast density, your health care provider may conclude you have dense breasts.
These mammogram images show a range of breast density.
Some breasts are mostly fat (fatty breasts) and some breasts are mostly breast and connective tissue (dense breasts).
Mammograms of dense breasts are harder to read than mammograms of fatty breasts.
Learn more about breast density and mammography.
Women with high breast density are 4-5 times more likely to get breast cancer than women with low breast density [100-101].
High breast density is common. In the U.S., 40-50 percent of women ages 40-74 have dense breasts [102-103].
Breast density varies greatly by age and weight. Dense breasts are more common in both young women and thin women [102-103]:
Medications that contain hormones can also affect breast density. For example :
Many states in the U.S. have laws requiring health care providers to notify (send a letter to) women found to have dense breasts on a mammogram.
Although this may seem helpful, there are no special recommendations or screening guidelines for women with dense breasts at this time.
Although women with dense breasts have an increased risk of breast cancer, it's not clear that lowering breast density will decrease risk.
For example, getting older and gaining weight after menopause are both related to a decrease in breast density, but an increase in breast cancer risk.
If you have any concerns about your breast density or your risk of breast cancer, talk with your provider.
Komen’s statement on breast density legislation
Susan G. Komen® endorses federal legislation requiring mammography centers to report breast density information to health care providers and patients.
Komen believes this legislation will improve the written mammography results providers send to patients. It requires the U.S. Food and Drug Administration (FDA) to consult with leading cancer organizations (including Komen) in the development of standard wording for these patient reports.
The legislation also directs the U.S. Department of Health and Human Services (HHS) to focus research on improving breast cancer screening methods.
At this time, there are no special recommendations or screening guidelines for women with dense breasts. However, your provider may suggest other types of breast imaging.
Digital mammography offers screening benefits over film mammography for women with dense breasts . Most mammography centers now use digital mammography to screen all women.
Learn about screening for women at higher risk of breast cancer.
Breast ultrasound, breast MRI and 3D mammography (each in addition to standard mammography) are being studied to learn whether they improve detection in women with dense breasts compared to standard mammography alone.
More research is needed to understand the benefits and harms of using any of these imaging tests (in addition to mammography) for women with dense breasts [106-107].
Learn more about breast ultrasound, breast MRI and 3D mammography.
*Please note, the information provided within Komen Perspectives articles is only current as of the date of posting. Therefore, some information may be out of date at this time.
Questions to Ask Your Doctor about Breast Density
Research Fast Facts