Dense Breast Tissue: What You Need to Know

When it comes to breast cancer screening, it goes without saying that mammograms remain the gold standard for early detection. This includes women with dense breast tissue. In addition, women with dense breast tissue (DBT) may consider supplemental screening – like dense breast ultrasound or breast MRI – along with a screening mammogram. If you’ve been told you have dense breasts, you’re not alone—nearly half of all women over 40 have some degree of breast density. But what does that mean, and why does it matter?

What Is Dense Breast Tissue?

Breasts are made up of glandular tissue, fibrous connective tissue, and fat. Dense breast tissue means there is more glandular and fibrous tissue and less fat. Because both dense tissue and certain signs of breast cancer appear white on a mammogram, it can be more challenging to detect cancer in women with DBT. The analogy is trying to find a snowflake in a snow storm.

Types of Breast Density

Radiologists classify breast density into four categories based on a mammogram:

A. Almost entirely fatty – The breasts contain mostly fat, making abnormalities easier to spot.

B. Scattered fibroglandular density – Some dense tissue is present, but most of the breast is fatty.

C. Heterogeneously dense – A significant amount of dense tissue is present, which can obscure small masses.

D. Extremely dense – The majority of the breast is composed of dense tissue, making it the hardest to assess using mammography alone.

Women with heterogeneously dense (type C) or extremely dense (type D) breasts are considered to have dense breast tissue, which can slightly increase the risk of developing breast cancer and make detection more difficult.

Note: type B tissue includes the word “density” in the terminology, but is not classified as “DBT” which can be confusing. Only types C and D are classified as dense breast tissue and benefit the most from supplemental screening.

Why Supplemental Screening May Be Helpful

Since dense tissue can mask certain signs of breast cancer, your healthcare provider may recommend additional breast imaging to improve cancer detection. Some common supplemental screening methods include:

• Breast Ultrasound: Uses sound waves to create images of breast tissue and can help detect cancers that may not be visible on a mammogram.

• Breast MRI (Magnetic Resonance Imaging): Provides highly detailed images and is especially beneficial for women at higher risk of breast cancer.

While these tests can improve detection, they are not replacements for mammograms. For example, these supplemental screens may not detect calcifications which can be one of the earliest signs of breast cancer; mammograms are very good at calcification detection, even when someone has DBT. The American College of Radiology recommends that every woman begin annual screening mammograms at age 40, and women with a family history of breast cancer begin screening much earlier.

The Bottom Line: Mammograms Are Still Essential

Even if you have dense breasts, mammograms remain the most important screening tool for early breast cancer detection. While they may not be as effective in detecting certain findings in dense tissue, they can still identify many cancers, including those in less dense areas of the breast.

If you have dense breasts, talk to your healthcare provider about your individual risk factors and whether supplemental screening  – in addition to mammography – may be right for you. Awareness and proactive screening can make all the difference in early detection and successful treatment.