Your Mammogram Report Now Tells You About Breast Density: The 2024 FDA Rule

What people see in the news

Since September 2024, people getting mammograms have been receiving a new piece of information: a statement about whether their breasts are "dense" or "not dense." A national FDA rule now requires it, and many were told for the first time that breast density is something worth knowing about.

What it actually means

Under the FDA's updated mammography regulations, enforcement of which began on September 10, 2024, mammography facilities must give every patient one of two standardized breast density notifications, and the report sent to the referring provider must include a density assessment. The rule creates a single national standard, replacing a patchwork of state laws.

So what is breast density? According to the National Cancer Institute, dense breasts have relatively high amounts of fibrous and glandular tissue and less fatty tissue. Density is determined by how the breast looks on a mammogram, not by how it feels. NCI notes dense breasts are common, especially in younger women, and that density tends to decrease with age.

Density matters for two reasons NCI describes. First, dense tissue can make it harder to see cancer on a mammogram, because both dense tissue and tumors appear white. Second, having dense breasts is itself associated with a modestly higher risk of breast cancer. The FDA's required wording reflects both points and encourages a conversation with a health care provider.

What this does and doesn't change

• The rule is about notification and transparency — making sure you're told your density and prompted to discuss it. It doesn't automatically add tests.
• Dense breasts are normal and common. Being told you have them is not a diagnosis and not cause for alarm.
• For some people with dense tissue, NCI notes that additional imaging (such as ultrasound or MRI) may be considered, but whether supplemental screening improves outcomes isn't fully settled, and it can add false positives. This is an individual decision.
• Mammograms remain valuable even for those with dense breasts — density is one factor among several to weigh with a clinician.

If you're not sure what to make of a density notification, our free screening check-up tool can help you prepare, and our overview of mammograms explains the basics.

Questions to ask a healthcare team

• What is my breast density category, and what does it mean for me?
• Given my density and overall risk, should I consider any additional imaging?
• What are the benefits and downsides of supplemental screening in my case?
• How often should I have mammograms?

Being told about breast density is meant to inform, not worry you. Free, plain-language cancer education helps more people understand what the new notification actually means.