Breast Tissue Composition and Clinical Significance

Breast Tissue Components

The upper outer quadrant and area under the areola and nipple contain the highest concentration of glandular tissue and are the most common sites for cancer to arise, according to the American Cancer Society 1, 2
Fibrous connective tissue contributes significantly to breast density on mammography, with increased stromal collagen associated with higher mammographic density and potentially increased breast cancer risk, as reported by the American College of Radiology 3, 4

Breast tissue is categorized into four density patterns according to the American College of Radiology BI-RADS atlas: almost entirely fatty, scattered fibroglandular elements, heterogeneously dense, and extremely dense 5, 7
Approximately half of women undergoing screening mammography have dense breast tissue (heterogeneously or extremely dense), which presents two challenges: reduced mammographic sensitivity and increased breast cancer risk, as noted by the American College of Radiology 5

Dense breast tissue (more fibroglandular components) can mask cancers on mammography, reducing sensitivity to as low as 30%, according to the Journal of the American College of Radiology 7, 5
Women with extremely dense breast tissue have a 4-6 fold greater risk of developing breast cancer compared to those with fatty tissue, as reported by the American College of Radiology 5
Understanding breast tissue composition is essential for appropriate screening recommendations and risk assessment, as emphasized by the American College of Radiology 5