Fibroglandular density refers to the proportion of fibrous connective tissue and glandular tissue compared to fatty tissue in the breast, as seen on a mammogram. It is a measure of breast tissue composition, where fibroglandular tissue includes the fibrous and glandular parts of the breast, such as milk glands and ducts, while fatty tissue is less dense
. Breast density is classified into four categories based on the amount of fibroglandular tissue:
- Almost entirely fatty: breast tissue is mostly fat, with little dense tissue (about 10% of women).
- Scattered fibroglandular density: mostly fatty tissue with some areas of dense tissue (about 40% of women).
- Heterogeneously dense: mostly dense tissue with some fatty tissue (about 40% of women).
- Extremely dense: almost entirely dense breast tissue (about 10% of women)
Fibroglandular density is important because dense breast tissue appears white on a mammogram, just like cancer, which can make it harder for radiologists to detect tumors. This phenomenon is called "masking." Additionally, higher breast density is associated with an increased risk of breast cancer
. In summary, fibroglandular density describes how much of the breast is made up of dense fibrous and glandular tissue versus fat, influencing both mammogram interpretation and breast cancer risk
