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In 2005, when she was 45 years old, JoAnn Pushkin was diagnosed with breast cancer. She had detected a lump and went to get a mammogram and an ultrasound. “I found out I had breast cancer, I found that I had dense breasts, and I found out the cancer had been missed because of dense breasts, all within 20 minutes of each other,” Pushkin tells PGN. Like Pushkin, almost half of U.S. women between the ages of 40 and 74 have dense breasts. While it’s common and normal, women with higher breast density have a higher chance of getting breast cancer, and dense tissue can make the cancer harder to detect on a mammogram. 

Pushkin’s cancer was advanced, so over the next few years she went through several surgeries and chemotherapy. After recovering, she wished she’d known about breast density and why it matters. “I didn’t know all the things that I should have known to be able to advocate for myself, for additional screening that might have led to an earlier stage diagnosis,” Pushkin recalls. Her experience led her to become a patient advocate and push for a law in her home state, New York, to notify women about their breast density. After the law was signed in 2012, she went on to advocate for a similar law at the national level. In 2015, she and radiologist and University of Pittsburgh professor Dr. Wendie Berg co-founded DenseBreast-info.org, an educational website. After over 10 years of advocacy, on March 9, the FDA announced a new rule that requires mammography facilities to include information about a patient’s breast density in their results. 

Read on to find out more about breast density and what to expect in your mammogram results following the FDA’s announcement. This article is meant for informational purposes and does not substitute for professional medical advice or conversations with your health care provider.

What is breast density?

Breast density is the amount of fibrous and glandular tissue in a person’s breasts compared with the amount of fatty tissue, according to the CDC. The more fibrous and glandular tissue breasts have, the denser they are. Fibrous and glandular tissue looks white on a mammogram. Yet a possible tumor also looks white on a mammogram—which means that cancers are harder to detect in dense breasts. 

In a mammogram report, breast tissue is put into one of four categories: 

  • Fatty: Is considered not dense and is found in about 10 percent of women.
  • Scattered: Is considered not dense and is found in about 40 percent of women. 
  • Heterogeneously dense: Is considered dense and is found in about 40 percent of women.
  • Extremely dense: Is considered dense and is found in about 10 percent of women. 

Why is it important to know if I have dense breasts?

Women with dense breasts have a higher risk of developing breast cancer. For example, women with extremely dense breasts have four times higher risk of breast cancer compared to women with fatty breasts. Additionally, having dense breasts makes it harder to detect cancers because dense tissue looks white on a mammogram, and so do calcifications and tumors.

How can I tell if I have dense breasts?

You can’t tell if you have dense breast tissue just by feeling your breasts. “Density has nothing to do with the way the breasts look or feel,” Berg tells PGN. “It is something that we can only tell on imaging, and the most common way we tell is from the mammogram.” 

Dense breasts can be hereditary, at least partly: “If a woman’s mother has dense breasts, she is more likely to have dense breasts, too,” Berg adds. 

(While doctors recommend being familiar with the way your breasts look and feel—and letting them know if you notice something abnormal—many medical organizations are no longer recommending routine breast self-exams because research hasn’t shown that self-exams improve cancer detection.) 

When should I get a mammogram?

Women with no risk factors should start annual mammograms at 40 years old. However, if you have a close relative who was diagnosed with breast cancer before age 50, it’s recommended that you start screening 10 years before your relative’s age of diagnosis, according to Berg. 

“So, if you have a mom diagnosed at 45, you should start at 35,” Berg says. “But beyond that, it is good to look at all the risk factors when you’re age 25 or so because if you do have a known mutation or genetic variant that causes increased risk of cancer, then you should start screening (with an MRI) at age 25.” 

If you’re at least 25 years old, the American College of Radiology recommends talking to your doctor about your individual risk factors to see if you should start early screening. 

What should I look out for in my mammogram results?

While your state may already have a law in place requiring notifying you about breast density, the FDA’s new rule means every state will now be required to do so. Starting on September 24, 2024, your mammogram results will include a notification about whether your breasts are dense. If they’re dense, the report will say so and will also note that “in some people with dense tissue, other imaging tests in addition to a mammogram may help find cancers.” 

What should I do if I have dense breasts?

Talk to your doctor about your risk factors and possible further testing. According to Berg, it’s important to consider other risk factors besides breast density. If you also have a family history of breast cancer or have had an atypical biopsy or breast cancer, you should ask your doctor for an MRI until you’re 70 years old. “And if you just have dense breasts and no other risk factors, then you may want to consider an ultrasound,” Berg adds. 

Overall, it’s important to ask your health care provider about your results. The National Cancer Institute suggests asking:

  • What are the dense breast-related findings on my recent mammogram?
  • Do you recommend additional screening or diagnostic tests for me?
  • What is my overall personal risk of breast cancer, given my risk factors and protective factors?

Will my insurance cover my mammogram?

If you live in the U.S., your screening mammogram—a test for people with no symptoms—should be free through your insurance if you’re 40 years or older. Coverage of additional testing, like ultrasounds and MRIs, depends on your state and your insurance

If you have symptoms (including a lump, pain, or discharge), your tests are considered diagnostic, which means you may have to pay a copay. If you’re uninsured, you may be eligible for free or low-cost screenings through the CDC’s National Breast and Cervical Cancer Early Detection Program

Resources for people with dense breasts: