Breast density is often grouped into four classifications using the Breast Imaging Reporting and Data System, or BI-RADS:
A—almost entirely fatty breast tissue, found in about 10 percent of women
B—scattered areas of dense glandular tissue and fibrous connective tissue (scattered fibroglandular breast tissue), found in about 40 percent of women
C—heterogeneously dense breast tissue with some areas of non-dense tissue, but most areas are dense with glandular tissue and fibrous connective tissue, found in about 40 percent of women
D—extremely dense breast tissue, found in about 10 percent of women
Breast tissue classified as C or D is considered dense.
This article first appeared in the October 2019 issue of UC Berkeley Health After 50.