A Closer Look: Breast Density and Cancer Detection

How dense are your breasts? It’s not something women think about until it’s time to screen for breast cancer. About 40 percent of women have dense breasts. What does it matter? Here’s what you need to know.

What are Dense Breasts?

Your breasts are made up of a mix of fibrous, glandular and fatty tissue. Dense breasts have a more fibrous or glandular tissue and less fat. This is not something you control with your diet. There is a genetic component as breast density is often inherited. 

How Do I Know if I Have Dense Breasts?

Breast density doesn’t have anything to do with how your breasts look or feel. The radiologist who reads your mammogram can determine your breast density, which falls into the four categories:

• Almost entirely fatty
• Scattered areas of fibroglandular density
• Heterogeneously dense
• Extremely dense

How Common are Dense Breasts?

One in 10 women have extremely dense breasts. On the other end of the spectrum, one in 10 women have entirely fatty breasts. The middle 80 percent fall somewhere in between with either scattered areas of fibroglandular density or heterogeneously (evenly) dense breasts. An estimated one in two women have what’s considered to be dense breasts.

Dense tissue appears white on a mammogram. Lumps - benign and cancerous – also appear white. That means mammograms can be less accurate in women with dense breasts because it’s more difficult to spot cancers. As a result, having dense breast tissue may increase your risk of getting breast cancer. 

Be Proactive with Your Care

Mammograms detect many cancers, even if you have dense breast tissue. So make sure you get your recommended mammogram. You should also talk to your doctor about whether you should have any additional screening exams. A newer technology called the Automated Breast Ultrasound (ABUS) finds up to 30% more cancers in dense breast tissue. What screenings you need is a decision you can make with your doctor weighing the pros and cons:

• Pro: Studies have shown that added imaging – ultrasound and MRI (magnetic resonance imaging) – can help find breast cancers that can’t be seen on mammograms.
• Con: Ultrasound and MRI are not always covered by insurance. They can also show findings that turn out not to be cancer, resulting in added testing and biopsies that may not be needed. 

As always, knowledge is power. To raise awareness of the impact of breast density on cancer detection, the majority of states in the US, including Nebraska and Iowa, have enacted legislation called the Dense Breast Disclosure Law to ensure the reporting of breast density to all women. When it’s time for breast cancer screening, know your breast density and discuss appropriate steps with your healthcare provider.

Take our Breast Health HRA (Health Risk Assessment) to find out your risk level.

Originallly posted September 2022. Reviewed October 2024