Why Dense Breasts Increase Breast Cancer Risk

A new study from the Oregon Health & Science University Knight Cancer Institute confirms what many experts have suspected for years: breast density plays a major role in both breast cancer risk and how well mammograms work. And for women with dense breasts, understanding that risk is crucial.

According to researchers, women with dense breast tissue are 1.7 times more likely to develop breast cancer compared to women with less dense breasts. Dense tissue also makes it harder for mammograms to detect abnormalities, which can lead to missed diagnoses and delayed treatment. This phenomenon, often called masking, means tumors can sometimes hide behind dense tissue.

Breast density refers to the balance between fatty and glandular tissue in the breast. Having dense breasts is common, especially among younger women, but it can make screening more complicated. According to the study, the sensitivity of digital mammography drops to 73% for women with extremely dense breasts compared to 93% for women with mostly fatty tissue.

Researchers analyzed data from over 33,000 women between 2000 and 2018 to separate two things: the actual risk of developing breast cancer and the likelihood of detecting it early. Their findings support recent updates requiring mammography centers to notify patients if they have dense breasts and explain how that impacts both screening and risk.

Starting September 2024, the Food and Drug Administration now requires every mammogram report to include information about breast density. For many women, this change opens the door to more informed conversations with doctors about personalized screening plans, including supplemental imaging like MRIs or ultrasounds.

The study highlights an important takeaway: knowing your breast density empowers you to make better decisions about your health. While dense breasts do not guarantee a cancer diagnosis, they do mean you need a more proactive approach to screening.