Dense breast tissue refers to the appearance of breast tissue on a mammogram. It's a normal and common finding.
On a mammogram, nondense breast tissue appears dark and transparent. Dense breast tissue appears as a solid white area on a mammogram, which makes it difficult to see through.
Levels of density are described using a results reporting system called Breast Imaging Reporting and Data System (BI-RADS). The levels of density are often recorded in your mammogram report using letters. The levels of density are:
A: Almost entirely fatty indicates that the breasts are almost entirely composed of fat. About 1 in 10 women has this result.
B: Scattered areas of fibroglandular density indicates there are some scattered areas of density, but the majority of the breast tissue is nondense. About 4 in 10 women have this result.
C: Heterogeneously dense indicates that there are some areas of nondense tissue, but that the majority of the breast tissue is dense. About 4 in 10 women have this result.
D: Extremely dense indicates that nearly all of the breast tissue is dense. About 1 in 10 women has this result.
In general, women with breasts that are classified as heterogeneously dense or extremely dense are considered to have dense breasts. About half of women undergoing mammograms have dense breasts.