Dense breast tissue is common, but it can hide other issues. Here’s what you need to know.

Published: December 12, 2023 | Updated: September 27, 2024

All breasts are unique – from their shape and size to their density. Breasts are made of fat, fibrous tissue (strands of collagen protein that hold fat, connective tissue and blood vessels in place) and glandular tissue (the part of the breast that makes milk). According to the Centers for Disease Control and Prevention (CDC), about 40% of women have some areas of density or are evenly dense throughout their breasts. Women with high breast density have a higher risk of developing breast cancer than women with low-density breasts.

What is breast density?

Breast density is determined by how much fibrous and fatty tissue you have. The more fibrous tissue you have, the denser your breasts are. Dense breast tissue can be seen on a mammogram, which is an X-ray picture of your breast tissue. It appears white, while fatty tissue appears black.  

Having dense breasts is a common condition. The CDC divides breast density into four categories:

A. The breasts are almost entirely fatty tissue (about 10% of patients).

B. A few areas of dense tissue are scattered through the breasts (about 40% of patients).

C. The breasts are made up of even amounts of dense tissue and fatty tissue, which is evenly spread throughout (about 40% of patients). This may be called “heterogeneously dense” on the mammography report.

D. The breasts are extremely dense (about 10% of patients).

The Relationship Between Breast Density and Breast Cancer

There is a connection between dense breast tissue and cancer. Research suggests that in general, the more dense breast tissue you have, the higher your breast cancer risk. It’s important to remember that most women are in the middle two categories of breast density (category B and C). For the 10% of women with extremely dense breast tissue (category D), breast cancer risk is about two times higher than for women who have dense breast tissue that is scattered throughout the breast (category B). For women who have consistent breast density (category C), the risk of cancer is about 1.5 times higher than that of a woman with scattered density (category B). 

These estimates also don’t take other personal breast cancer risk factors into account such as family history or lifestyle factors such as smoking. High breast density by itself isn’t enough to put you into a high-risk category for breast cancer. Your health care provider will look at your overall health to help you understand what your risk for developing breast cancer is with dense breasts.

There does not seem to be an increased chance of death from breast cancer in women with dense breasts. Even though you have denser breasts, you are not more or less likely to die from breast cancer than women without dense breasts. 

Importance of Annual Breast Cancer Screenings

Breast density can change somewhat over time. It can be affected by:

• Age: Older women tend to have lower breast density than younger women.
• Menopause: This is the most common time for breast density to change.
• Hormone therapies: These can affect breast density in most women.

All these changes can impact how your health care provider reads your mammogram — it can be difficult to see tumors growing in dense breast tissue. 

Yearly mammograms are especially important for women with dense breast tissue. Breast cancers can be seen on a mammogram, but some cancers are more difficult to catch if you have this type of dense breast tissue. Mammograms combined with regular breast self-examinations can help you know what your breasts normally look and feel like, so it’s easier to see and feel changes. 

If you have other risk factors for breast cancer, such as the presence of a genetic mutation or strong family history of breast cancer, your health care provider may want you to start having mammograms earlier than age 40 or more often than once per year. 

Talk to your doctor about your breast cancer risk. Be sure to go to annual checkups with your health care team, and see which breast cancer screenings are right for you. 

Best Imaging Techniques for Dense Breasts

A mammogram typically uses X-rays to get a picture of the breast, but dense breast tissue makes it difficult to see tumors with regular mammography. Fibrous tissue appears white on an X-ray, as do masses or clumps of cancer cells.

• 3D mammogram: Also called breast tomosynthesis, 3D mammography is the most advanced imaging technique available. It uses X-rays to capture thin images of the breast, which are then combined to create a detailed three-dimensional image.
• Breast ultrasound: This test uses sound waves and their echoes to make computer pictures of the inside of the breast. It can show certain changes, like fluid-filled cysts, that can be harder to see on mammograms.
• Breast MRI: Magnetic resonance imaging is usually reserved for women at increased risk, including those with certain genetic mutations or a strong family history of breast cancer.

Communication With Health Care Providers

Most states require your provider to tell you in your mammogram report if you have dense breasts. Talk to your health care provider about:

• Family history of breast cancer
• Family history of dense breasts
• Results of any genetic testing you have done
• What breast cancer screening would be best for you

Lifestyle and Risk Reduction

Research shows there is a definite link between dense breast tissue and cancer. While there is no cure for breast cancer, there are things you can do to reduce your breast cancer risk, even if you have dense breasts, including:

• Diet: Eating whole grains, vegetables, fruit and lean meats is a good way to reduce cancer risk, especially if you have dense breasts.
• Exercise: Moderate physical exercise most days of the week for about 30 minutes can reduce your risk for breast cancer.
• Alcohol: Limiting or eliminating alcohol reduces your chance of developing breast cancer. Studies suggest limiting alcohol to one drink per day for women and two drinks per day for men or less can reduce the risk for several types of cancer.
• Weight: Maintaining a healthy weight decreases cancer risk by reducing the body’s exposure to certain hormones. 

Your breast health is important. Talk with your health care provider about scheduling a mammogram, practice monthly breast self-exams and make positive lifestyle changes. Breast cancer screening is the best way to detect cancer in dense tissue and stay on top of your health.