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Everyone’s breasts are different, made up of a unique combination of fat, milk glands, ducts, and fibrous connective tissue. Your individual combination of these types of tissues affects the density of your breasts.
Radiologists define breast density in four categories:
- Almost entirely fatty: No dense breast tissue is visible on the mammogram.
- Scattered areas of fibroglandular density: Mostly fatty tissue, with some dense tissue.
- Heterogeneously dense: Mostly dense tissue with some fatty tissue.
- Extremely dense: Almost entirely dense breast tissue.
Women whose breasts fall into the third or fourth categories are considered to have dense breasts. Having dense breasts is normal, and there’s nothing you can or should do to change it. But breast density is something you should be aware of.
Dense breasts are common. Between 40-50% of women in the U.S. from age 40 to 74 have dense breasts.
If you have dense breasts, it can make cancer more difficult to detect with a mammogram, because fibroglandular tissue and cancer can look similar. Women who have dense breasts are also at a slightly higher risk of developing breast cancer than those who do not.
New regulations from the U.S. Food and Drug Administration (FDA) set to go into effect in September are intended to standardize how mammography results are communicated. The change is meant to help women understand the density of their breast tissue and how it might impact their risk of developing breast cancer.
Many states, including Maryland and D.C., already require radiologists to notify women about the density of their breasts. At MedStar Washington Hospital Center, we talk about breast density with our patients all the time. Here are some common questions we discuss.
1. What is the new FDA requirement regarding breast density?
The Mammography Quality and Standards Act was federal legislation adopted in 1992 to make sure all mammograms are high quality and follow strict standards. It established the FDA as the agency in charge of oversight of mammography.
In 2023, a change to the act required that all women who have had a mammogram receive a notice about the density of their breasts. All facilities performing mammograms must begin including the FDA’s standard language in their reports as of September 10, 2024.
MedStar Health will switch to this new language soon. If you are a patient, you may have already heard from us about this change.
2. What causes dense breasts?
Factors that can impact your breast density include:
- Genetics: If your mother had dense breast tissue, you’re likely to as well.
- Age: Younger women tend to have more dense breast tissue.
- Menopause: Hormonal changes can cause dense fibroglandular tissue to shrink.
- Medications: Some hormone therapies can impact your breast density.
- Body mass index: Women with less fatty tissue overall tend to have less fatty tissue in their breasts.
While we’re not sure why some women have more dense breasts than others, it is entirely normal to have breasts of any density.
3. How do I know if I have dense breasts?
The only way to know the density of your breasts is with a mammogram. When we image the breast, fatty tissue appears transparent or dark. Fibroglandular tissue appears white on a mammogram. The reason this is important is because cancer can appear white on a mammogram, too, which can make it more difficult to detect.
4. Does having dense breasts increase my risk of cancer?
Yes. Experts consider the slight increase in risk of developing breast cancer equal to the risk of having a single relative with a history of breast cancer. It’s important to understand that while having dense breast tissue slightly increases your risk of cancer, it does not mean you are at high risk.
You should discuss your individual cancer risk factors with your doctor so you can make an informed decision about the best screening methods for you.
Related reading: What Does it Mean If I Am “High Risk” for Breast Cancer?
5. Should I still get mammograms if I have dense breasts?
Yes. Mammography is the best test for detecting breast cancer early. What’s more, mammography is the only imaging test that has been shown to decrease your risk of dying from breast cancer.
The American College of Radiology recommends that women at average risk of developing breast cancer should start getting a mammogram every year when they turn 40. That’s the guideline we use at MedStar Washington Hospital Center.
While dense breast tissue can make it trickier to tell fibroglandular tissue from cancer, there are secondary signs we can see in the image that make mammography a very useful tool for detecting breast cancer. In addition, all women at MedStar who have a mammogram receive a 3D mammogram, also known as digital breast tomosynthesis, which can be particularly helpful in detecting breast cancer in women with breast dense tissue.
6. Are other imaging techniques better for dense breasts?
If you are at high risk for developing breast cancer and you have dense breasts, your doctor may recommend a breast MRI. Breast ultrasound is an additional screening that has been shown to help detect cancer, particularly in women with dense breasts.
It is important to know, however, that these tests do not replace mammography. They can be complimentary to mammograms in helping to reveal small cancers that may hide among dense tissue. But these imaging methods aren’t perfect—they can return false-positive results. This can lead to additional testing, such as additional mammogram pictures required or even a breast biopsy that is later shown to not be cancer.
Related reading: Advances in Breast Cancer Care Mean More Hope and Survivorship for Patients.
Breast density knowledge is power.
The FDA’s new regulation will help more women know whether they have dense breast tissue so they can make better informed decisions about their care. Talk with your healthcare team to understand your risk of breast cancer and understand what screenings are available for you.
