June 24, 2019

How breast density affects your cancer risk

The letter arrives announcing that your recent mammogram was fine (cue huge sigh of relief) but your breast tissue was classified as dense. So what does that mean, and why does it matter?

“Dense breasts refers to the appearance of breasts on a mammogram,” explains Mai A. Elezaby, MD, a UW Health radiologist who specializes in breast imaging. “It is affected by the ratio of fat cells compared to glands and tissues in the breast. Approximately 50 percent of women who get mammograms have dense breasts.”

Your breast tissue density has always been included in the formal mammogram report received by your doctor. But you may not have known about your breast density until recently: In 2018, Wisconsin passed legislation requiring providers to notify patients who have dense breasts, a trait that can impact your breast cancer screening.

Breast density is classified into four categories:

  • almost entirely fatty

  • scattered areas of fibroglandular density

  • heterogeneously dense

  • extremely dense

The last two categories are considered “dense” breasts, which can make cancer detection more difficult.

“Dense breast tissue appears as areas of white on a mammogram, which is very similar to what cancer looks like,” Elezaby explains. “So in traditional 2D mammography, increased breast density may hide cancer.”

How breast density affects your cancer risk

Here’s what to know about breast density and how it affects your cancer risk.

Breast density can change. While breast density can be influenced by genetics, diet (particularly a Western-style diet high in fat and refined grains), alcohol consumption, hormonal treatments, and age can also play a role. “A lot of factors might affect the appearance of our breasts on mammograms,” Elezaby says. “Dense breasts are more often seen in younger women. As we get older and the circulating female hormones decrease, the density of the breast tissue might be less over time.”

Dense breasts can increase cancer risk. Not only does dense breast tissue make cancer more difficult to detect in the early stages — it might also predispose you to developing cancer. “Comparing the least dense to most dense breasts, it increases your risk of developing breast cancer by four fold,” Elezaby notes. But the risk for breast cancer is not just based on one factor. Other risk factors include older age, increased body weight, lifestyle choices, family history, and known genetic mutations, the BRCA1 or BRCA2 genes being the most common.

Talk to your doctor about mammogram frequency. While doctors used to recommend starting annual mammograms at age 40, there’s been a movement to wait longer. “We know that annual screening starting at 40 gives us the best results, but it does have slightly more drawbacks, such as false positives,” she says. “Still, starting the conversation at age 40 is important.”

Elezaby recommends getting at least one baseline exam between ages 40-45. If you have dense breasts and other risk factors, your doctor may recommend annual mammograms instead of every other year.

Ask about 3D mammography. “Some improvements in technology, such as 3D mammography, also known as digital breast tomosynthesis-DBT, may help with screening dense breasts,” she says. “It doesn’t completely correct for it, but it improves looking through the breast tissue a little bit. 3D mammography is not the standard of care, but if you think you have dense breast tissue, you can advocate for 3D technology.”

You may need other screening tools. “We’re also looking at other technologies, such as ultrasound and MRI. These additional screening tools may help in overcoming the limitations of mammography, and there’s a lot of research going on right now on what is the best supplementary tool,” she says. “But many of the supplemental tools are not fully covered by insurance.” Because there’s the most long-term data on mammography, it continues to be the standard of care.

Don’t wait if you notice any breast changes. Women with dense breast tissue tend to have a more difficult time with self breast exams, making it even more important to stay on top of regular screenings. “If you notice any changes definitely be proactive and promptly see your doctor,” Elezaby says. “If you find cancer earlier, that gives us a bigger chance for a complete cure, in addition to fewer treatments, which translate to fewer complications, less health care costs, and less time away from family or off work.”

Maintain a healthy lifestyle. Regardless of your breast density level, it’s wise to do what you can to lower your cancer risk. “Obesity, excessive alcohol intake and hormone therapy can all increase your risk of breast cancer, so it’s also important to discuss health and lifestyle choices with your clinicians,” she says.

Don’t stress. “I think it’s important for patients not to freak out if they have dense breasts,” Elezaby says. “About half of us have dense breasts, and it’s a very normal thing.”