Dense Breast Tissue Guide

What Is Breast Density?

Breast tissue is made up of glandular tissue, fibrous connective tissue, and fat. "Dense" breasts have more glandular and fibrous tissue relative to fat. Breast density is assessed on a four-category scale (ACR categories A–D) and is reported in mammogram results in many countries.

How Common Is It?

Approximately 40–50% of people who have mammograms are found to have dense breast tissue. It is more common in younger people and tends to decrease with age, though it can persist after menopause.

Why It Matters for Screening

Dense tissue appears white on a mammogram — so does cancer. This means that cancer can be harder to detect on standard mammography in dense breasts. Supplemental screening methods such as ultrasound or MRI may be recommended for people with very dense breasts and other risk factors.

What to Do

If your mammogram report mentions dense breast tissue, discuss with your doctor what supplemental screening, if any, is appropriate for your individual risk profile. In many US states, radiologists are now required to inform patients if they have dense breast tissue.