Fibroglandular tissue is a normal component of the breast, contributing to its structure and function. It is a natural part of breast anatomy that varies among individuals and is not indicative of disease. Understanding fibroglandular tissue aids in comprehending breast health and medical imaging.
Components and Function
Fibroglandular tissue comprises two primary types: fibrous connective tissue and glandular tissue. Fibrous connective tissue provides support and shape to the breast, acting as a framework. This dense tissue is similar to the material found in ligaments and scar tissue.
Glandular tissue consists of lobules and ducts, which are specialized structures involved in milk production and transport. Lobules are small glands responsible for producing milk, while ducts are tiny tubes that carry milk from the lobules to the nipple. These components facilitate lactation when stimulated by hormones during pregnancy. Fatty tissue fills the spaces around the fibroglandular components, contributing to the breast’s size and shape.
Fibroglandular Tissue and Breast Density
The amount of fibroglandular tissue relative to fatty tissue determines breast density, a characteristic assessed during mammography. Breasts with more fibroglandular tissue than fatty tissue are considered dense. Breast density is a common finding, affecting approximately half of women over 40 years old, and it is not considered a disease. Radiologists categorize breast density using the Breast Imaging Reporting and Data System (BI-RADS), which outlines four levels:
- Category A: Almost entirely fatty, with very little dense tissue.
- Category B: Scattered areas of fibroglandular density, describing breasts that are mostly fatty with some scattered dense tissue.
- Category C: Heterogeneously dense, signifying most of the breast tissue is dense, though some areas of fatty tissue are still present.
- Category D: Extremely dense, meaning nearly all breast tissue is dense with very little fatty tissue.
Categories A and B are considered non-dense or low-density breasts. Categories C and D are considered dense breasts. Breast density often decreases with age, although this change is not universal for all women.
Implications for Breast Screening
The amount of fibroglandular tissue carries important implications for breast cancer screening, particularly with mammography. Dense fibroglandular tissue and cancerous masses both appear white on a mammogram. This creates a “masking effect,” where dense tissue obscures potential tumors, making them harder to detect. This reduces mammography’s sensitivity in individuals with higher breast density.
Despite this challenge, mammography remains the primary screening tool for breast cancer due to its proven ability to reduce mortality rates. For individuals with very dense breasts (categories C and D), supplemental screening methods may be recommended to improve cancer detection. Additional tests, such as breast ultrasound or magnetic resonance imaging (MRI), can help identify cancers hidden by dense tissue. Supplemental screening decisions are discussed with a healthcare provider, considering individual risk factors.