Breast density refers to the relative amounts of dense fibroglandular tissue (glandular and fibrous connective tissues) compared to nondense fatty tissue as seen on a mammogram. Breast density is a key factor in breast health. You cannot tell if your breasts are dense by how they look or feel.
Categories of breast density
Radiologists classify breast density into four groups based on the appearance on a mammogram:
- Almost entirely fatty — The breasts contain primarily fatty tissue, making it easier to detect tumors. About 10% of women fall into this category.
- Scattered areas of fibroglandular density — About 40% of women fall into this category.
- Heterogeneously dense — There are areas of the breast that are dense, where it can be hard for the radiologist to see cancer if present. This category applies to about 40% of women.
- Extremely dense. Most of the breast appears dense, which can frequently hide cancer if present. Approximately 10% of women have extremely dense breasts.
Women in the heterogeneously dense or extremely dense categories have “dense breasts.” Women with fatty or scattered density are “not dense.”
It is now a national standard that your mammogram result letter will include whether your breasts are “dense” or “not dense.” The specific density category is included in the mammogram report to your health care provider.
Why Does Breast Density Matter?
Dense breasts matter because of the effects on both breast cancer risk and mammogram accuracy. The denser the breasts, the greater the risk of cancer going unseen on the mammogram. There is also a greater risk of developing breast cancer.
Women with denser breasts are also more likely to be called back for additional testing for findings that are not cancer, called false alarms or false positives.
Having dense breasts:
- Makes cancer harder to detect — Dense breast tissue appears white on a mammogram — like tumors — making it harder to detect some cancers. This can delay diagnosis and treatment. Fatty tissue, on the other hand, appears dark, making tumors easier to spot.
- Increases breast cancer risk — Dense breast tissue increases the risk of developing breast cancer, probably because cancers develop in glandular tissue, and dense breasts have more glandular tissue.
It is always important to be aware of any changes in your breasts, but this is particularly true in dense breasts, even after a normal or “benign” mammogram. If you notice a new lump or skin dimpling, you should see your doctor and probably have a breast ultrasound.
You should review other risk factors with your doctor, such as:
- Family history of breast cancer, including ages at diagnosis.
- Hormone use.
- Known or suspected disease-causing genetic variants.
- Prior breast biopsies, especially if “atypical.”
- Prior radiation treatment to the chest before age 30.
Women at high risk, even if they do not have dense breasts, should start screening MRIs as early as age 25 and continue MRI every year until at least age 70.
If you have extremely dense breasts, or if you have heterogeneously dense breasts and other risk factors, or if you have already been treated for breast cancer, you may be recommended to have additional screening with breast MRI.
Talking to your doctor about your screening options and staying proactive about breast health through regular checkups and healthy lifestyle choices will improve your chances of lowering breast cancer risk.
What Causes Dense Breast Tissue?
Several factors contribute to breast density, including:
- Age — Younger women are more likely to have dense breast tissue, which may decrease around menopause.
- Body weight — Leaner women are more likely to have dense breast tissue. A lower body mass index (BMI) has a higher proportion of dense breast tissue due to less fatty tissue in the breasts.
- Genetics — If your mother or sister has dense breasts, you’re more likely to have dense breast tissue, too.
- Hormones — Estrogen and progesterone levels affect breast density. Women taking hormone supplements may experience increased density.
Steps for Breast Health
- Talk to your doctor about your breast cancer risk and whether additional screening is necessary. Risk assessment is ideally performed by age 25 as some women at high risk should start breast screening with MRI by age 25.
- Maintain yearly mammograms starting at age 40 and follow recommended screening guidelines. Remember, early detection is key in the fight against breast cancer. If you have dense breasts, it’s especially important to stay on top of your screenings and to follow up with your health care provider if you have any concerns or questions.
- Maintain breast self-exams and awareness. While breast self-exams have not been shown to reduce breast cancer mortality, they help you become more familiar with your body and notice any changes. If you detect any lumps, pain, or changes in appearance, report them to your health care provider right away.
- Know your family history. If you have a family history of breast cancer or other risk factors, consider discussing genetic testing (such as testing for BRCA mutations) with your doctor. This test analyzes your risk level and guides decisions about screening and prevention.
- Consider lifestyle changes, such as a healthy diet, exercise, and reducing alcohol intake. Some guidelines:
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- Exercise regularly — Physical activity is shown to lower the risk of breast cancer. Aim for at least 150 minutes of moderate exercise each week, including activities like walking, jogging, swimming, or strength training.
- Maintain a healthy weight — Obesity after menopause increases the risk of breast cancer. Eat a balanced diet with plenty of fruits, vegetables, and whole grains, and limit processed foods to manage your weight.
- Limit alcohol intake — Alcohol consumption increases the risk of breast cancer—the more alcohol you consume, the greater your risk. Reducing or avoiding alcohol intake altogether can help lower your risk.
- Avoid hormone replacement therapy (HRT) — If you are postmenopausal, discuss the risks and benefits of HRT with your health care provider. Some forms of hormone therapy increase the risk of breast cancer, particularly when combined with dense breast tissue.
- Eat a breast-friendly diet — A diet rich in antioxidants (found in fruits, vegetables, and whole grains) and healthy fats (like omega-3s from fish or nuts) can help protect against cancer. Some studies suggest a plant-based diet may lower breast cancer risk.
- Quit smoking — Smoking slightly increases the risk of breast cancer, particularly in premenopausal women. If you smoke, quitting improves your overall health.
Understanding the implications of dense breast tissue is crucial for effective breast cancer screening and early detection. Women with dense breasts should engage in informed discussions with their health care providers to tailor a screening plan that considers their risk factors and breast density.
Find additional information about dense breast tissue at DenseBreast-info, Inc. | Dense Breast Tissue Information Resource.
Editor's Note: This article was originally published on , and was last reviewed on .
Sources
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NCI Dictionary of Cancer Terms. National Cancer Institute. Link. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/heterogeneously-dense-breast-tissue
Dense Breasts: Answers to Commonly Asked Questions. National Cancer Institute. Link. https://www.cancer.gov/types/breast/breast-changes/dense-breasts
Molly Adams. Dense breast tissue: What it is, and what to do if you have it. MD Anderson Cancer Center. Link. https://www.mdanderson.org/cancerwise/dense-breast-tissue--what-it-is--and-what-to-do-if-you-have-it.h00-159539745.html