An Introduction to Dense Breast Tissue

5 Facts to Know

1. Breast density is determined through a woman’s mammogram and described as one of four categories depending on the amount of breast tissue in comparison to fat in the breast.
2. 40% of women age 40 and over have dense breasts.
3. Cancer is 4 times more likely in women with extremely dense breasts than in women with fatty breasts.
4. Though mammograms find some cancers not seen on other screening tests, in dense breasts, mammograms will miss up to 40% of cancers present. As density increases, the effectiveness of mammography decreases.
5. Other screening tests, such as ultrasound or breast MRI, in addition to mammography substantially increase detection of early stage breast cancers in dense breasts.

Cancer in a Mammogram of a Fatty vs. Dense Breast (below)

Dense Breast Tissue Categories (below)

(A) Fatty; (B) Scattered fibroglandular density; (C) Heterogeneously dense; (D) Extremely dense

How do you answer the question “Are you dense?” Breasts which are (C) heterogeneously dense, or (D) extremely dense on mammography, are considered “dense breasts.”

Print the Patient Fact Sheet