For many women, a mammogram provides more information than whether breast cancer is present. It also provides a picture of the breast tissue itself, including whether the breasts are made up mostly of fatty tissue or dense tissue.
Dense breast tissue is very common. Nearly half of women age 40 and older who have mammograms in the United States have dense breasts.
Knowing your breast density can help you better understand your mammogram and, along with other risk factors, have a more informed conversation with your healthcare provider about breast cancer screening.
Flavia Posleman Monetto, MD, a breast imaging radiologist at The University of Texas Medical Branch (UTMB Health), explains what breast density means, how it can affect a mammogram, and when additional imaging may be considered.
What dense breast tissue means
Breast density is determined by how breast tissue appears on a mammogram.
“When a woman has a mammogram, there is usually a combination of dark and white areas,” Posleman Monetto said. “The dark areas are mostly fatty tissue, while the white areas represent dense fibrous and glandular tissue. When there is a larger amount of dense tissue, we call the breasts ‘dense.’”
That difference matters because dense breast tissue and many breast cancers both appear white on a mammogram.
“The more dense tissue there is, the more difficult it can be to see something that is also white, including some breast cancers and calcifications,” she said. “It can be like trying to see a small object on the road while driving on a foggy day or trying to see the stars through a cloudy sky.”
When the surrounding breast tissue is mostly fatty, it appears dark on a mammogram, creating greater contrast with a white abnormality. When there is more dense tissue, that contrast can be reduced, making some abnormalities more difficult to detect.
How common are dense breasts?
Dense breasts are common, particularly among younger women. Breast density tends to decrease with age, although not for everyone. Genetics, body weight, and hormone replacement therapy also can influence breast density.
Because nearly half of women age 40 and older who undergo mammography have dense breasts, breast density is an important part of breast health for many women.
“Patients can sometimes become very worried when they hear that they have dense breasts,” Posleman Monetto said.
But having dense breasts does not necessarily mean a woman is at high risk for breast cancer. Density is one piece of a much larger picture.
Density is one piece of the risk picture
Breast density matters for two reasons. First, dense tissue can make some cancers harder to see on a mammogram. Second, dense breast tissue itself is an independent risk factor for developing breast cancer.
“Having dense breasts does increase a woman’s risk of developing breast cancer, but it does not automatically mean that she is at high risk,” Posleman Monetto said.
That distinction is important. Learning that you have dense breasts does not automatically mean you need additional imaging after a normal mammogram.
The decision about supplemental screening depends on breast density, overall breast cancer risk, medical history, and the potential benefits and limitations of additional testing.
Doctors may consider factors such as family history, previous breast biopsies, a personal history of breast cancer, genetic mutations, and prior radiation exposure. Risk assessment tools can combine these factors to estimate a woman’s overall risk.
For women whose calculated lifetime risk is 20% or greater, the American College of Radiology recommends annual breast MRI in addition to mammography.
What does Texas law require?
For women in Texas, information about breast density is now a routine part of the mammography experience.
Texas’ breast density law, originally enacted in 2011 and known as Henda’s Law, was updated effective Sept. 1, 2025, to align state requirements with federal breast density reporting standards. The required notification explains that dense tissue can make breast cancer harder to detect and can also increase the risk of developing breast cancer.
Federal regulations have required mammography facilities to include breast density information in mammography reports and patient notifications since Sept. 10, 2024.
So, if a mammogram report says you have dense breasts, what should you do with that information?
Understanding your next steps
Having dense breasts is common and does not necessarily mean you are at high risk for breast cancer. Understanding your breast density alongside your other risk factors can help make informed decisions about screening.
“Breast density is just one piece of the picture,” Posleman Monetto said. “The important thing is to know your breast density, understand your risk, keep up with your recommended mammograms, and talk with your healthcare provider about the screening approach that is right for you.”
Schedule time with a Women's Health Specialist to stay on top of your screenings.