Understanding Breast Density
Breasts are made up of a mixture of fibrous and glandular tissue and fatty tissue. Your breasts are considered dense if you have a lot of fibrous or glandular tissue but not much fat. Density usually decreases with age. Breast density is determined by the radiologist who reads your mammogram and will be included in your imaging report. In fact, under the NJ Breast Density Law, reports must include information about breast density. The legislation also requires insurers to cover follow-up evaluations, such as ultrasound or MRI, in women with dense breast tissue.
Why is breast density important?
Dense breasts do make it more difficult for doctors to spot cancer on mammograms. Having dense breast tissue may increase your risk of getting breast cancer.
How do I know if I have dense breasts?
Breast density is determined by the radiologist who reads your mammogram. There are four categories of mammographic density. The radiologist assigns each mammogram to one of the categories. Your doctor should be able to tell you whether you have dense breasts based on where you fall on the density scale.
If I have dense breasts, do I still need a mammogram?
Yes, a mammogram is the only medical imaging screening test proven to reduce breast cancer deaths. Many cancers are seen on mammograms even if you have dense breast tissue.
Are there any tests that are better than a mammogram for dense breasts?
In breasts that are dense, cancer can be hard to see on a mammogram. Studies have shown that ultrasound and magnetic resonance imaging (MRI) can help find breast cancers that can’t be seen on a mammogram. These are supplemental examinations intended to be used in conjunction with mammography to increase the ability to detect breast cancer in extremely dense breast parenchyma.
What should I do if I have dense breasts?
If you have dense breasts, talk to your doctor. Together, you can decide which, if any, additional screening exams are right for you.
For a referral to a RWJBarnabas Health primary care physician or breast specialist, call 888-724-7123.
What New Jersey Law Regarding Breast Density Means for Patients and Physicians
New Jersey state law requires all women to be notified of their breast density and provides for additional screening coverage for women with extremely dense breasts.
Breast density on mammography refers to the relative density of fibroglandular tissue vs. fat. The greater the amount of fibroglandular tissue (seen as white on mammograms) vs. fat (seen as gray), the greater the chance of a breast cancer hiding from sight. Also, since breast cancer develops primarily from glandular tissue and ducts, the greater the amount of fibroglandular tissue, the greater the substrate for developing cancer.
The American College of Radiology defines breast density on mammograms in four categories:
- Almost entirely fatty: 10 percent of women
- Scattered areas of fibroglandular tissue: 40 percent of women
- Heterogeneously dense tissue: 40 percent of women
- Extremely dense tissue: 10 percent of women
Those women with "extremely dense" breasts have two times the risk of developing breast cancer than the average female population. As per the new law, those women with this category of density are eligible for additional methods of screening for breast cancer, covered by insurance.
The additional methods can help to detect cancer that may not be seen on mammograms. The main two supplementary methods are whole-breast ultrasound and breast MRI. Ultrasound is preferable for women with an average risk for developing breast cancer, while for women at high risk, such as women with a family history of breast cancer, MRI is a better choice.
Please note that these supplementary tests are in conjunction with and don't replace mammography, which remains the main screening tool.
Additional online resources include:
- American College of Radiology at acr.org
- American Cancer Society at cancer.org
- Are You Dense Advocacy at areyoudense.org
