Most people are fairly familiar with their breasts, be they big or small, firm or soft. But what if your doctor tells you that you have dense breasts?

Contrary to how it sounds, having dense breasts doesn’t have anything to do with size. Rather, it has to do with the makeup of your breast tissue itself.

“Breast density is identified on a mammogram. It’s not something you can determine during a physical exam at your doctor’s office,” says Janie Lee, MD. Dr. Lee is a professor of radiology at the University of Washington and clinical director of breast imaging at Seattle Cancer Care Alliance. Within our breasts, we have:

• Fatty tissue.
• Glandular tissue. This is where our milk ducts are.
• Fibrous tissue. It holds everything together.

Having dense breasts is common. “About half of all women have dense breasts,” says Dr. Lee. Transgender women are also likely to have dense breasts. The research is light, but one small study found that 60% of transgender women who have hormone therapy also develop dense or very dense breasts.

Unfortunately, there are some health risks that come with having dense breasts. Dense breasts put people at higher risk of breast cancer. People with 50% or higher breast density are 3 times more likely to be diagnosed with breast cancer than those with less than 10% breast density. Doctors aren’t exactly sure why.

Another concern: Breast cancer is harder to spot in a mammogram of a denser breast. Signs of cancer and dense breast tissue both look white on a mammogram.

In good news, people with dense breasts are not more likely to die from breast cancer than people with fattier breasts. But it’s important to know your breast density and stay on top of your screenings. That can help you catch any concerns early, when cancer is generally easier to treat. Here’s what you need to know.

How to Know if Your Breasts Are Dense

Breast density falls into 4 categories. The categories are defined by the Breast Imaging Reporting and Data System (BI-RADS). It was developed by the American College of Radiology:

• A: Almost entirely fatty. Nearly the entire breast appears as gray tissue. Fat looks gray on a mammogram.
• B: Scattered areas of fibroglandular density. The areas of dense glandular tissue and fibrous connective tissue look white. Most of the mammogram looks gray where there is fat.
• C: Heterogeneously dense. This means there’s a higher amount of white tissue than gray. It may make it hard to see small masses.
• D: Extremely dense. This means there’s mostly white tissue on the mammogram. It lowers the sensitivity of mammography.

Your breasts are dense if they fall within the C or D category. Learning that your breasts are dense might seem frightening at first. But Dr. Lee stresses that it doesn’t automatically mean you’re on track to get breast cancer. “Breast density is only one of several risk factors,” says Dr. Lee. “It’s important to talk to your doctor about all your breast cancer risk factors.”

Breast density is typically included in the mammogram report given to your doctor. But not all patients get that information. Several states (but not all) have passed legislation requiring that people be notified directly of their breast density. It’s important to confirm this information with your doctor.

Knowing your breast density can hopefully help guide more accurate screening results in the future.

What Screening Options Look Like for Dense Breasts

If you’ve been told you have dense breasts, the mammogram process will still be the same in the future. You’ll still have to get your breasts squeezed in a mammography machine to create an image. But the type of images that are taken might be different. It depends on what mammography type your cancer center uses.

Mammogram machines can take either 2D or 3D digital images. Along with a 2D mammogram, more healthcare facilities are also offering 3D mammograms as part of routine mammography appointments. Also known as digital breast tomosynthesis, 3D mammograms are often more precise. They allow for an exam of thin sections of breast tissue. They also offer the views of the whole breast that you’d get with a standard 2D mammogram.

Also, 3D mammograms have been shown to find the same breast cancers that 2D mammograms can, but with fewer false positives. (False positives are false alarms that turn out not to be breast cancer.) If you have dense breasts, your doctor may suggest that you get both a 3D and 2D mammogram.

What if My Radiologist Finds an Area of Concern?

If there’s a significant finding on your screening mammogram, your radiologist may recommend more imaging tests afterward. These may include:

• An ultrasound. This is also known as a sonogram. It uses sound waves to investigate problem areas in the breast.
• Magnetic resonance imaging (MRI). This may also be used to look for cancer after a mammogram with negative results.

Ultrasounds and MRIs both raise the likelihood of finding a cancerous tumor that a mammogram might miss. They may also raise the chances of false positives.

Breast density alone doesn’t mean you need more screenings. But doctors often recommend an MRI screening with mammography in people known to be at high risk. That includes people with dense breasts. It also includes those who carry genetic mutations that raise their breast cancer risk. Your radiologist will talk with your doctor about your breast cancer risk level. They’ll decide which screening tools are best for you, says Dr. Lee.

Remember, breast density is just one piece of the puzzle in breast cancer screenings. And it can be used to take more control of your health, says Dr. Lee. “Even though breast density makes things a bit more complicated, it’s encouraging. Considering individual factors like breast density is part of a more personalized approach to medicine.”

[Sources:]

[1] Gooren LJ, van Trotsenburg MAA, Giltay EJ, et al. “Breast Cancer Development in Transsexual Subjects Receiving Cross-Sex Hormone Treatment.” The Journal of Sexual Medicine, vol 10, no. 12, December 2013, pp: 3129-3134.

[2] “Women with Dense Breasts Have Higher Risk of More Aggressive Cancer.” BreastCancer.org, August 1, 2011, https://www.breastcancer.org/research-news/20110801. Accessed January 3, 2022.