Breast density is determined by the doctor (a radiologist) who examines the mammogram images. The radiologist can also use computer software to measure (quantify) the breast density. Breast density is not determined by how a breast looks or feels. The density is categorized as one of four categories (see below) and is usually in the report sent from the radiologist to the referring doctor.
A woman’s breast tissue is described on mammography as one of four categories:
(A) Fatty; (B) Scattered fibroglandular tissue; (C) Heterogeneously dense; (D) Extremely dense
Breasts which are (C) heterogeneously dense, or (D) extremely dense, are considered “dense breasts.”
A. ALMOST ENTIRELY FATTY – On a mammogram, most of the tissue appears dark gray or black while small amounts of dense (or fibroglandular) tissue display as light gray or white. Such breasts are not considered dense.
About 10% of all women have breasts considered to be “fatty.”
B. SCATTERED AREAS of FIBROGLANDULAR DENSITY – There are scattered areas of dense (fibroglandular) tissue mixed with fat. Even in breasts with scattered areas of breast tissue, cancers can sometimes be missed when they look like areas of normal tissue or are within an area of denser tissue. Such breasts are not considered “dense.”
About 40% of all women have breasts with scattered fibroglandular tissue.
C. HETEROGENEOUSLY DENSE – There are large portions of the breast where dense (fibroglandular) tissue could hide masses. Such breasts are considered “dense.”
About 40% of all women have heterogeneously dense breasts.
D. EXTREMELY DENSE – Most of the breast consists of dense (fibroglandular) tissue creating a “white out” situation, making it extremely difficult to see through and making the detection of some cancers difficult. Such breasts are considered “dense.”
About 10% of all women have extremely dense breasts.