What is breast density?
Breast density describes the ratio of fibrous and glandular tissue to fatty tissue in your breasts. On a mammogram, denser tissue appears white like many cancers which makes it harder to spot changes.
The American College of Radiology's Breast Imaging Reporting and Data System (BI-RADS) is used to describe breast density seen on the mammogram. The levels of density, which are included in a mammogram report are:
A. Almost entirely fatty means that the breasts are almost entirely made up of fatty tissue. There is very little dense breast tissue.
B. Scattered areas of fibroglandular density means the breasts are mostly made up of fatty tissue. But there are some scattered areas of dense breast tissue.
C. Heterogeneously dense means that most of the breast tissue is dense breast tissue. But there are some areas of fatty tissue.
D. Extremely dense means that nearly all of the breast tissue is dense breast tissue. There is very little fatty tissue.
If your results are in categories C or D we say that you have dense breast tissue.
How common are dense breasts?
- Nearly 50% of women aged 40 and older who get mammograms are found to have dense breast tissue.
- It’s more common in women who have a lower BMI or who take hormone therapy for menopause.
- Density can change over time with your age, hormones or other health factors.
Why breast density matters
Dense breast tissue matters for two reasons:
- Cancer detection is more challenging. Dense breast tissue can obscure cancers on a mammogram, making them harder to detect early. It may also make it more difficult to feel abnormalities during a self-exam.
- Differences in risk level. Dense breast tissue is linked to a modest increase in breast cancer risk as compared to someone without dense breast tissue. But on its own, having dense breast tissue does not give you a high risk of breast cancer, but a risk similar to someone who has a relative who had the disease. Having dense breast tissue does not increase the risk of dying of breast cancer.
How you’ll know if you have dense breasts
Only a mammogram can determine density. You can’t tell by touch or by looking. In Massachusetts, radiologists are required by law to notify you if your mammogram shows dense breast tissue. This ensures you can follow up with your doctor.
If your mammogram shows dense breasts:
- Talk with your doctor about your full risk picture. Family history, genetics and lifestyle all play a role.
- Stay consistent with screening mammograms. They remain the most effective first step.
- Consider additional imaging. All Tufts Medicine locations use 3D mammography (tomosynthesis), which provides a more detailed view of breast tissue compared to traditional 2D mammograms. If your results are difficult to interpret, your doctor may also recommend additional tests, such as an MRI<.
- Make a personalized plan. Your care team will help you decide what’s right for you.
Quick FAQs
| Question | Answer |
|---|---|
| Does having dense breasts mean I’ll get cancer? | No. Dense breasts are common and only slightly raises risk. |
| Is a mammogram still useful? | Yes. It’s still the best starting point for screening. |
| Will I always need extra tests? | Not necessarily. It depends on your overall risk. |
The bottom line
Dense breast tissue is common and manageable. Knowing your density is an empowering step toward protecting your health. Your clinician can help guide you with clear answers and compassionate care so you can feel confident in your screening plan.
