The phrase “scattered areas of fibroglandular density” on a mammogram report can be confusing, but it is a standardized way for radiologists to describe the composition of your breast tissue, not an abnormality. This finding refers to the specific proportion of different tissue types visible on the X-ray image. Understanding this common detail is the first step toward informed peace of mind and effective breast health monitoring.
Understanding Fibroglandular Tissue and Breast Density
Breast tissue is composed of three primary components: fatty tissue, glandular tissue, and fibrous connective tissue. Fatty tissue is translucent to X-rays, appearing dark or nearly transparent on a mammogram image. Glandular tissue (milk ducts and lobules) and fibrous tissue (structure) are both dense and appear white on the X-ray.
The term “fibroglandular density” is the collective term for this dense combination of glandular and fibrous tissues. The relative amount of this dense tissue compared to fatty tissue determines your overall breast density score. This ratio is measured and reported by a radiologist after reviewing the mammogram.
A high amount of fibroglandular tissue results in dense breasts, while a high amount of fatty tissue results in less dense breasts. Breast density is not related to the size or firmness of the breast, and it can only be accurately assessed through a mammogram. Density usually decreases naturally with age, though some women maintain higher density throughout their lives.
Interpreting the “Scattered Areas” Finding
The American College of Radiology uses the Breast Imaging Reporting and Data System (BI-RADS) to classify breast density into four categories. The term “scattered areas of fibroglandular density” corresponds to Category B, the second-lowest density level. This follows Category A, which is almost entirely fatty tissue. Approximately 40% of women fall into this Category B designation, making it a very common finding.
This description means your breasts are predominantly composed of fatty tissue, but there are isolated, small pockets of the denser fibroglandular tissue dispersed throughout the breast. Since the majority of the tissue is fatty, Category B breasts are generally not considered “dense” in the context of requiring supplemental screening. This finding is simply a measurement of normal tissue composition.
How Density Affects Mammogram Readability
The practical implication of breast density relates to the visual contrast on a mammogram image. Both cancerous tumors and fibroglandular tissue absorb X-rays and appear white on the film. In a predominantly fatty breast, which appears dark, a white tumor stands out clearly, similar to a white object against a dark background.
In breasts with higher density, large areas of white fibroglandular tissue can visually obscure a potential tumor, an effect known as masking. However, the low volume and dispersed nature of the “scattered areas” finding create a minimal masking effect. The mammogram’s readability remains high because a large percentage of the image is still the dark, transparent fatty tissue.
This is a key distinction from Categories C (heterogeneously dense) and D (extremely dense), where extensive white tissue creates significant challenges for a radiologist to detect a small mass. For women with Category B density, the challenge of a tumor being masked is low, confirming that this is considered a low-level density finding. Tracking density is important because tissue composition can change over time.
Next Steps for Screening and Monitoring
For women with a finding of scattered areas of fibroglandular density and no other elevated risk factors, the standard annual screening mammogram is typically sufficient for monitoring. This low-level density does not usually warrant additional, routine supplemental screening tests. Tests like breast ultrasound or MRI are generally reserved for women in denser categories (C or D) or those with a high personal risk profile.
Discuss your mammogram report and personal risk factors with your healthcare provider. Your provider can combine the density finding with other factors, such as family history or genetic markers, to determine the most appropriate screening schedule. Maintaining a consistent annual screening schedule and performing regular self-exams remain the most effective actions for early detection.