Your Mammogram Letter Says 'Dense Breasts.' Do You Need an MRI or Ultrasound?

Since September 10, 2024, every mammogram facility in the U.S. must tell you in your results letter whether your breast tissue is dense.¹ Here’s what that means and what to ask next.

What “dense” means

Your report puts your breasts in one of four categories:¹

1. Almost entirely fatty
2. Scattered areas of dense tissue
3. Heterogeneously dense, which may hide small masses
4. Extremely dense, which lowers the mammogram’s accuracy

The last two count as dense. The required letter explains that dense tissue makes cancer harder to see and raises the risk of breast cancer, and that other imaging tests may help find cancers in some people.¹

What the Task Force says

The U.S. Preventive Services Task Force recommends a mammogram every 2 years from 40 to 74.² For extra ultrasound or MRI after a normal mammogram in women with dense breasts, it says the evidence is insufficient to weigh benefits against harms.² That isn’t a “no,” just a statement that the research isn’t complete.

What the biggest trial found

In the Netherlands, about 40,000 women aged 50 to 75 with extremely dense breasts and a normal mammogram were split into groups; some were invited to have an MRI.³

• Cancers found between screenings dropped from 5.0 to 2.5 per 1,000 in the MRI-invitation group.³
• MRI found 16.5 cancers per 1,000 women scanned.³
• But about 8 in 100 had a false alarm, and about 1 in 4 biopsies found cancer.³
• Only 59% of invited women chose the MRI.³

The trial’s main measure was cancers found between screenings over two years, not deaths from breast cancer.³

Questions to ask

1. Which density category am I, and what’s my overall breast cancer risk?
2. Would ultrasound or MRI add enough for me to be worth false alarms?
3. What would it cost, and does my plan cover supplemental imaging?
4. Should I keep screening after 75? The Task Force says evidence is insufficient there too.²

Our guides to hormone therapy and breast screening, mammograms with implants and deodorant before a mammogram cover related questions.

Try: “My letter says I have extremely dense breasts. Given my risk, would an MRI or ultrasound help, and will insurance pay for it?”

My Body Changed. Now What? includes a Visit Brief. Use it to note your density category, family history and screening dates before your next visit. See the book.