What are the four classifications of breast tissue composition based on the ratio of fatty to glandular tissue?

The classification of breast tissue composition is important for understanding mammographic density, which can influence the risk of breast cancer and the visibility of lesions on mammograms. The four classifications—fatty, fibrofatty, fibroglandular, and glandular—reflect a spectrum of breast tissue composition.

Fatty tissue consists primarily of adipose tissue, which appears less dense on mammograms. Fibrofatty tissue contains both fat and some fibrous or glandular components, striking a balance that can still show some density. Fibroglandular tissue has more glandular and fibrous elements relative to fatty components, making it denser and potentially more challenging to interpret on imaging. Finally, glandular tissue consists almost entirely of fibroglandular elements, which are very dense and can obscure the identification of abnormalities on mammograms.

This classification system is based on the relative proportions and types of tissue, which is critical for radiologists interpreting mammograms and assessing breast cancer risk. Understanding these classifications helps clinicians determine the appropriate screening strategies based on tissue density, as denser breast tissue can mask potential tumors.