Scattered areas of fibroglandular density is a breast density classification that appears on mammogram reports. It means your breasts are mostly made up of fatty tissue, with some patches of denser glandular and fibrous connective tissue mixed in. About 40% of women who get mammograms receive this classification, making it the most common category alongside heterogeneously dense tissue.
If you’re reading this, you likely just got a mammogram result and want to know what this phrase means for your health. The short answer: it’s a normal finding, not a diagnosis, and it doesn’t place you in the “dense breast” category that prompts additional screening conversations.
How Breast Density Categories Work
Radiologists classify breast tissue into four categories using a system called BI-RADS, developed by the American College of Radiology. These categories describe how breast tissue appears on a mammogram, where fatty tissue looks dark and dense tissue looks white. The four levels are:
- Category A: Almost entirely fatty tissue (about 10% of women)
- Category B: Scattered areas of fibroglandular density (about 40% of women)
- Category C: Heterogeneously dense, meaning dense tissue is spread fairly evenly throughout (about 40% of women)
- Category D: Extremely dense (about 10% of women)
Scattered fibroglandular density falls into Category B. On the mammogram image, you’d see a mostly dark background (the fatty tissue) with some lighter white patches scattered throughout. Those white areas are the fibroglandular tissue, a mix of milk-producing glands and the connective tissue that supports them.
What You Can and Can’t Feel
Breast density is purely a mammographic finding. It describes how tissue looks on imaging, not how your breasts feel when you touch them. A woman with dense breasts on a mammogram may have soft, unremarkable-feeling breasts, and a woman with mostly fatty tissue might feel lumps or firmness from other causes. The only way to know your breast density category is through a mammogram.
Scattered Density and Cancer Risk
When doctors and researchers talk about breast density as a risk factor for cancer, they’re primarily focused on Categories C and D. Those two groups are formally classified as “dense breast tissue.” Category B, scattered fibroglandular density, is grouped with Category A as “nondense.”
This distinction matters because density affects mammogram accuracy in two ways. First, dense tissue appears white on a mammogram, and so do tumors. When there’s more dense tissue, small cancers can hide behind it. Second, having more glandular tissue is itself associated with a modestly higher cancer risk. But with scattered density, most of the breast is still fatty, so these effects are significantly less pronounced than in Categories C or D.
Research from the Breast Cancer Surveillance Consortium found that mammograms catch about 88% of cancers in women with nondense breasts (Categories A and B combined), compared to about 78% in women with dense breasts. For context, the detection rate for extremely dense breasts specifically drops to around 67% compared to 92% for almost entirely fatty breasts. Scattered density sits comfortably in the higher-performing range.
Screening Recommendations for Category B
Standard mammography screening is generally considered sufficient for women with scattered fibroglandular density. The conversations about supplemental screening with ultrasound or MRI focus on women in Categories C and D. Even for those denser categories, experts haven’t reached full agreement on which additional tests are most beneficial, since supplemental imaging can flag findings that turn out not to be cancer, leading to extra biopsies and anxiety.
There’s one important exception: if you have other risk factors for breast cancer, such as an inherited gene mutation like BRCA1 or BRCA2, a strong family history, or a history of chest radiation at a young age, your doctor may recommend MRI screening alongside your mammogram regardless of your density category. Those recommendations are based on your overall risk profile, not density alone.
Why Your Report Includes This Information
Many states now require mammogram facilities to notify patients about their breast density. This is why you’re seeing this language on your report even though scattered fibroglandular density isn’t a medical concern on its own. The notification laws were designed primarily to alert women with dense breasts (Categories C and D) that mammograms may be less effective for them, but the reports typically include density information for all categories.
Your density category can also change over time. Breast tissue tends to become less dense with age, particularly after menopause, as glandular tissue is gradually replaced by fatty tissue. Hormone replacement therapy can increase density. So the category on one mammogram may not match what you see on a future one.
What This Means in Practical Terms
If your mammogram report says “scattered areas of fibroglandular density,” you’re in the second-least-dense category out of four. Your mammograms are effective at detecting abnormalities, and you don’t fall into the “dense breast” group that triggers discussions about supplemental screening. Continue with your regular mammogram schedule, and keep in mind that this classification describes tissue composition, not a health problem. It’s simply part of the standard information radiologists report when reading your images.