Breast density: Meaning in a Radiology Report

Also written as: breast composition, mammographic density, dense breasts, dense breast tissue

Breast density describes how much of the breast is dense glandular tissue rather than fat on a mammogram, in four categories from A to D.

What it means

Breast tissue is a mix of fat and fibroglandular tissue (milk glands, ducts and supporting tissue). On a mammogram, fat looks dark and dense tissue looks white. Radiologists sort density into four categories: A, almost entirely fatty; B, scattered areas of dense tissue; C, heterogeneously dense; and D, extremely dense. C and D count as dense breasts. Density is seen on the mammogram, not felt by touch.

When it matters

Dense breasts are common and normal, found in about half of women who have mammograms. They matter for two reasons. Small cancers also look white, so dense tissue can hide them on a mammogram. Dense breasts also carry a somewhat higher risk of breast cancer. Density often decreases with age. Depending on your overall risk, your doctor may discuss extra screening, such as ultrasound or MRI.

Questions to ask your doctor

Which density category am I, and has it changed since my last mammogram?
Given my density and risk, would extra screening help me?
Does my density change how often I should have mammograms?

General information, not medical advice. What a finding means for you depends on your symptoms, your history and the images themselves, so talk your results through with a doctor.