Dense breast tissue can add a layer of complexity when it comes to evaluating and diagnosing breast cancer in women. The presence of dense tissue may make it more difficult to detect abnormalities in the breast and can be associated with an increased risk of breast cancer. Dense breast tissue is found in more than 40% of women, and density can change year over year. Knowing more about breast density and the importance of annual mammograms in identifying these changes can help women maintain their best breast health over time.
What Is Dense Breast Tissue?
Breasts are made of milk glands and ducts, connective tissue, and fat, all of which make up your breast density. Breast density is essentially the ratio of glandular and connective tissue to fatty tissue. Breast density isn’t something that can be measured by feel. It can only be identified and categorized through a mammogram.
Breast density is measured by the Breast Imaging Reporting and Data System (BI-RADS) scale, which was created by the American College of Radiology. The levels of density are rated on a letter scale. Here are the levels of the BI-RADS scale:
- A: The breast is almost entirely fatty tissue. This level is found in around 10% of women.
- B: There are scattered areas of glandular and connective tissue, but most of the breast is fatty tissue. Around 40% of women have scattered density.
- C: Most of the breast contains dense glandular tissue but there are some areas of fatty tissue, which is known as heterogeneously dense. About 40% of women have this level.
- D: The breast is almost entirely connective and breast tissues with very little fatty tissue. Around 10% of women have extremely dense breasts.
You are more likely to have a higher breast density if you are a young woman, pregnant or breastfeeding, are taking hormone replacement therapy, or if you have a lower body weight.
While researchers aren’t clear on what causes dense breasts, women can often inherit dense breasts. Additionally, the density of your breasts can change over time, and as you age or gain weight, your breasts may lose some of their density.
Dense Breasts and Cancer Risk
Higher breast densities — category C (heterogeneously dense) or D (extremely dense) — are associated with an increased risk for breast cancer, primarily because these breast tissue types can hide or conceal cancers. Because dense breasts make it difficult to read traditional mammograms, high breast density can mask early-stage breast cancer, making it harder to detect. If you have dense breasts, keep up with your annual mammogram screenings to detect subtle changes in your breast tissue or density over time.
Advanced 3D mammography is recommended for screening because it can help better characterize breast density and identify breast cancers early. 3D mammographic imaging captures “slices” of the breast, layering the images to create a 3D view that is clearer and easier for a radiologist to read.
In addition to an annual 3D mammogram, women with higher breast density may benefit from additional imaging such as:
- Breast ultrasound
- Breast MRI
These are all advanced imaging exams that can improve breast cancer detection in women with dense breasts and have been shown in clinical studies to be effective when used in combination with mammography.
Breast Cancer Screening Recommendation
According to the National Comprehensive Cancer Network, women with an average risk for breast cancer should start annual mammogram screenings at age 40. For women who are at a higher risk for breast cancer, the NCCN recommends starting mammogram screenings sooner. If you are at high risk for breast cancer, you should talk to your physician about a screening schedule that is right for you.