Does Breast Density on a Mammogram Matter?
By Jennifer Footit-Tank, BSN, RN, CCP, quality care coordinator at Network Health
10/21/2025
A federal mandate in 2024 requires all mammogram results inform the patient about their breast density or breast thickness. Breast density tells you the amount of fibrous and glandular tissue compared to fatty tissue in your breast. Breast density has nothing to do with how full or saggy your breasts are. It is based on what a radiologist sees on the mammogram.
So why should this matter to you? You may have seen this on a mammogram and had that exact question. The simple answer is that denser breasts are at a slightly higher risk for developing breast cancer, and it can make cancer detection more difficult. Of course, it isn’t as clear cut as that.
Categories of Breast Density and What They Mean
There are four categories of density based on the Breast Imaging Reporting and Data System (BI-RADS):
- Level A: Almost entirely fatty – not dense breast
- Level B: Scattered fibroglandular densities – not dense breast
- Level C: Heterogeneously dense – dense breast
- Level D: Extremely dense – dense breast
Half of all women are diagnosed with dense breast tissue, or levels C and D. Dense breasts do not mean there is anything wrong. It’s a natural variation.
Research is unsure why dense breasts have an increased chance of developing into breast cancer. Dense tissue also makes reading the mammogram more difficult because dense tissue looks the same as breast masses. Radiologists are trained to detect the differences.
But modern imaging techniques have also improved detection for breast cancer for both dense and non-dense breasts. The most common types are digital mammography and digital breast tomosynthesis or 3D mammography. Mammography remains the most effective method for breast cancer screening.
What Causes Dense Breasts?
Breast tissue density is not caused by a single reason. Some contributing factors include the following.
- Age – breasts are denser in your 20’s and 30’s, becoming less dense as you age
- Weight – a lower body mass index (BMI) usually means higher breast density
- Family history – genetics may be a link to breast density; if other women in your family have denser breasts you may be similar
- Hormone replacement medication – taking hormones after menopause is associated with higher breast density
- Giving birth – lower breast density is linked childbirth
- Tamoxifen – taking this medication to treat or prevent certain breast cancers can lower breast density
There is no treatment needed for dense breasts but there does need to be an awareness. If your mammogram results show you are a Level C or D, discuss this with your health care provider to get your questions answered.
Your medical provider will discuss your risk with you based on age, breast density, family history and other risk factors to determine frequency and the type of screening that will best meet your needs.
Early detection is critical because 1 in 8 women develop breast cancer according to the American Cancer Society.
Questions about your plan or would like to talk to a nurse? Call us at Network Health
