Dr. Alison Chetlen, left, chief of breast imaging radiology at Penn State Health Milton S. Hershey Medical Center, positions a patient for a mammogram.
For women ages 40 and above, mammograms are the best way to detect breast cancer early, when the disease is most treatable. Mammograms also reveal another important detail: whether you have dense breasts and might benefit from additional breast cancer screening.
“Having dense breasts is normal – it means your breasts contain more tissue than fat,” says , chief of breast imaging radiology at and professor of radiology at . “However, for women with dense breasts, mammograms alone may not be enough to detect breast cancer.”
The reason? Women with very dense breasts are four to six times more likely to develop breast cancer than women with non-dense breasts. Breast cancer is also more difficult to detect in dense breast tissue.
What are dense breasts?
Breasts contain fat and fibroglandular tissue–fibrous material and milk-producing glands. Each woman’s breasts vary in the percentage of fat versus fibroglandular tissue, Chetlen said. Breast density is described in one of four different categories :
- Dense breasts: mostly fibroglandular tissue
- Heterogeneously dense breast tissue: mostly dense tissue with some fat
- Scattered fibroglandular density: mostly fat with some dense tissue
- Non-dense breasts: mostly fat
About 40% of women ages 40 to 74 have dense breasts. Genetics are the top reason. You can’t tell whether your breasts are dense based on how they look or feel. Only imaging tests can confirm it. On a mammogram, dense breast tissue looks white, while fat appears gray, Chetlen said.
Why are dense breasts linked to breast cancer risk?
Breast cancer is more common, yet harder to find, in dense breasts. Over 70% of breast cancers occur in dense breast tissue. In extremely dense breasts, up to 50% of cancers might be missed.
“On a mammogram, dense tissue and masses both appear white, so a suspicious mass may be hidden in dense tissue,” Chetlen said. “Dense breast tissue causes a masking effect, making it difficult for radiologists to effectively read your mammogram–like finding a snowball in a snowstorm.”
Breast cancers in women with dense breasts also tend to be more advanced, requiring more extensive treatment, Chetlen said.
How do I find out if I have dense breasts?
Since September 2024, the U.S. Food and Drug Administration has required mammogram reports to inform patients whether their breasts are dense.
“Patients now get to have the critical information to communicate with their providers, make joint decisions and advocate for themselves,” said , a researcher at and professor of surgery and chief of surgical outcomes, research and quality at Penn State College of Medicine.
Some states–including Pennsylvania–have required breast density notification for years. Shen received a $100,000 grant from the PA Breast Cancer Coalition in January to study how these state laws affect patient outcomes.
“Our goal is to uncover critical insights into how these policies are affecting breast cancer detection and care,” Shen said.
What should I do if I have dense breasts?
If you find out you have dense breasts, you have options. “Now you’re empowered with this information, and you can choose what to do with it,” says Chetlen.
Shen agrees. “Patients can talk with clinicians about whether they should take supplemental screening, and that can have downstream effects like the timeliness of breast cancer diagnosis, the stage of cancer when they get diagnosed, and treatments and outcomes,” she said.
What other screening options are available?
If you have dense breasts, your doctor might recommend supplemental breast cancer screenings. “Supplemental screening can help us find those nonpalpable, small, invasive cancers before they metastasize,” Chetlen said. Early detection can reduce the need for aggressive treatments like surgery and chemotherapy.
One option is automated whole breast ultrasound, a noninvasive test that uses sound waves to create a detailed 3D picture of your breast. When automated whole breast ultrasound is used with mammography, breast cancer detection improves by 35.7% over mammography alone.
This screening test differs from a diagnostic breast ultrasound, which is used to examine abnormalities found in previous tests. Diagnostic breast ultrasounds give doctors a clearer picture of masses or other changes, helping them and patients decide on the best treatment. Diagnostic mammograms can also be used to explore unusual findings. For women with a very high breast cancer risk, based on genetics, family history or health history, a breast MRI is often recommended as well.
“Talk to your doctor about your options, and together, you can make an informed decision,” Chetlen said.
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