Breast Cancer

Dense Breasts 101: What You Need to Know if You Have This Type of Breast Tissue

If you have dense breast tissue, you’re at higher risk for breast cancer and your breasts will be harder to screen via mammograms. Here’s what you need to know to navigate risk and screening.

Julie Lynn Marks
By
Preeti K. Sudheendra, MD
by
Updated on May 10, 2024
mammogram showing dense breasts vs non-dense breasts
Dense breasts make it harder to spot cancers on mammograms.Shutterstock (2)

Regular screening with mammograms is generally the best way to catch breast cancer early. But for some women, there's a catch: dense breast tissue — which may elevate your risk for breast cancer and may make it difficult to spot cancers on mammograms.

What are Dense Breasts?

Ryland Gore, MD, explains what dense breasts are and what you should be aware of if you have them.
What are Dense Breasts?

Next up video playing in 10 seconds

What Are Dense Breasts?

Breasts are made of fat and glandular tissue (milk glands and ducts) held together by fibrous tissue.

 Dense breasts contain relatively more glandular and fibrous tissue compared with fatty tissue.

 The only way to discover this is by having a mammogram.
There are four categories that radiologists use to describe breast tissue. You have dense breasts if you fall into the latter two:

  • Fatty Mostly fatty tissue (about 10 percent of women)
  • Scattered Fibroglandular Mostly fatty with some fibrous and glandular tissue mixed in (about 40 percent of women)
  • Heterogeneously Dense Large areas of fibrous and glandular tissue (about 40 percent of women)
  • Extremely Dense Mostly fibrous and glandular tissue (about 10 percent of women)

What Causes Dense Breasts? 

Researchers don’t know exactly why some women have dense breasts and others don’t.

Many times, the density of breast tissue are inherited. However, you may be more likely to have dense breast tissue if you:

  • Have less body fat
  • Are younger
  • Are pregnant or breastfeeding
  • Take or have taken hormone therapy for menopausal symptoms
  • Have smaller breasts

Who Has Dense Breasts?

Having dense breasts isn't unusual, especially in young women. In fact, about one-half of women under age 50 have dense breasts.

 And while density tends to decrease with age as estrogen levels decline, the change tends to be moderate, says Wendie Berg, MD, PhD, a radiologist at the University of Pittsburgh School of Medicine–UPMC.
Dr. Berg estimates that about 25 percent of women in their sixties still have dense breasts.

 Research has also shown that Asian women are more likely to have dense breast tissue compared with women of other ethnicities.

Breast Cancer Risk and Dense Breasts

Berg says there are several reasons dense breasts increase the risk of cancer, but a big factor is that cancer develops in the glandular tissue. “The glandular tissue is a lot of what appears dense on a mammogram,” she explains. “The more glandular tissue, the greater the risk of developing breast cancer.”

Having dense breast tissue isn't as big a risk factor as something like inheriting a genetic mutation like BRCA1 or BRCA2, but it's not insignificant. And, the greater the density, the higher the risk.
Research shows women with very dense breasts are 4 times to 5 times more likely to develop breast cancer compared with those with fatty breasts.

Though having dense breasts raises the risk of breast cancer, research shows density does not mean women are more likely to die of the disease.

In one study, researchers found women who developed breast cancer had a significantly slower decline in breast density compared with those who didn’t develop breast cancer.

Dense breasts also increase risk by making it more difficult to spot cancer on a mammogram. When radiologists look at a mammogram image, fatty breast tissue shows up as transparent and easy to see through. However, dense breast tissue appears solid white, which is the same color as breast cancer. The dense tissue is difficult to see through, which is why some breast cancers could be missed. Some describe this as trying to pick out “a snowball in a blizzard.”

How to Find Out if You Have Dense Breasts

In the past, most women did not know if they had dense breasts. At the moment, 39 states plus DC have enacted legislation that requires women to be notified about their breast density after having a mammogram, cites DenseBreast-Info. And in March 2023, the U.S. Food and Drug Administration (FDA) updated their guidelines to require that all facilities notify women about the degree of their breast density on a mammogram report. 

 These new requirements will go into effect in September 2024.

Additional Screening for Dense Breasts?

Mammograms still detect many cancers, even in women with dense breasts, says Berg. But if you have dense breasts, your doctor may recommend that you have an ultrasound or MRI (magnetic resonance imaging), in addition to a mammogram, to thoroughly screen for breast cancer.

Women who have a lifetime risk of breast cancer of 20 percent or higher should get a mammogram and MRI every year, according to the American Cancer Society.

Berg’s own breast cancer went undiagnosed because it could not be seen on a mammogram due to dense tissue. She pushed for an MRI that detected early stage breast cancer and has since founded the website DenseBreast-Info to educate both patients and clinicians about this issue.

“Do not wait for your doctor to recommend additional screening if you have dense breasts. Not all doctors are aware of the issues,” Berg says. “Advocate for yourself. My own cancer was only caught early because I knew to request an MRI.”

One caveat: MRIs and ultrasounds are more sensitive tests, which make them better at detecting cancers in dense breasts than mammograms, but their sensitivity also means they have a higher rate of false positives (test results that look positive for cancer but are proven wrong by subsequent tests).

Editorial Sources and Fact-Checking

Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.

Sources

  1. Breast Density on a Mammogram. Susan G. Komen. April 4, 2023.
  2. 5 Facts to Know. DenseBreast-Info.
  3. Dense Breast Tissue: What It Means to Have Dense Breasts. Mayo Clinic. March 9, 2024.
  4. What Does It Mean to Have Dense Breasts? Centers for Disease Control and Prevention. July 25, 2023.
  5. What Are Dense Breasts? DenseBreast-Info.
  6. What Does It Mean to Have Dense Breasts? Roswell Park Comprehensive Cancer Center. October 13, 2023.
  7. Advani SM et al. Association of Breast Density With Breast Cancer Risk Among Women Aged 65 Years or Older by Age Group and Body Mass Index. JAMA Network Open. August 26, 2021.
  8. Do Black Women Have Denser Breasts? Do Asian Women Have Denser Breasts? Do Hispanic Women Have Denser Breasts? DenseBreast-Info.
  9. Jiang S et al. Longitudinal Analysis of Change in Mammographic Density in Each Breast and Its Association With Breast Cancer Risk. JAMA Oncology. April 27, 2023.
  10. Berg W. The FDA’s Rule Change Requiring Providers to Inform Women About Breast Density Could Lead to a Flurry of Questions. UPMC. April 7, 2023.
  11. American Cancer Society Recommendations for the Early Detection of Breast Cancer. American Cancer Society. December 19, 2023.
Show Less