Levels of Density
A universal reporting system for levels of density, called the Breast Imaging Reporting and Data System (BI-RADS), uses the letters A, B, C and D to indicate your level of breast density. This is often recorded in mammogram reports by the radiologist reviewing your images.
These levels of density indicate:
A: The breasts are almost entirely composed of fat. About 1 in 10 women has this result.
B: There are scattered areas of fibroglandular density, but the majority of the breast tissue is non-dense. About 4 in 10 women have this result.
C: There are some areas of non-dense tissue, but the majority is dense. About 4 in 10 women have this result.
D: Nearly all breast tissue is dense. About 1 in 10 women has this result.
Women whose level of breast density is C or D are usually considered to have dense breasts.
You may be more likely to have dense breasts if you:
- Are young. Breast tissue tends to become less dense as you age, though some women may have dense breast tissue at any age.
- Take hormone therapy for menopause. Women who take combination hormone therapy to relieve signs and symptoms of menopause are more likely to have dense breasts.