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Dense Breasts? Here’s What You Need to Know

Your mammogram report may warrant a follow-up conversation with your doctor

spinner image  woman wearing a hospital gown, getting her annual mammogram, technologist in background
kali9/Getty Images

American journalist Katie Couric doesn’t just get mammograms. In September 2022, the former NBC host and CBS anchor revealed in an article on her website that her routine breast cancer screenings often involve an extra step. 

Because she has dense breasts, she also gets a breast ultrasound. A recent ultrasound she underwent detected early-stage breast cancer.

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Like Couric, many women in the U.S. are informed about their breast density — some states require doctors to notify patients if they have dense breasts. And starting in September 2024, all mammography facilities in the U.S. will be obligated to do the same, thanks to a new rule issued by the Food and Drug Administration (FDA). 

Here’s what you need to know about dense breasts and how the FDA’s rule may change your mammogram follow-up care.

What is dense breast tissue?

There are three different types of tissue in the breast — fibrous, glandular and fatty. Your breast density reflects the amount of fibrous and glandular tissue (or fibroglandular tissue) in your breast, compared with the amount of fatty tissue. “The more glands and fibrous tissue that a woman has, the denser her breast tissue is,” says Megan Kalambo, M.D., an associate professor in the Department of Breast Imaging at the University of Texas MD Anderson Cancer Center.

Dense breast tissue isn’t something you can see or feel yourself, but it shows up on a mammogram. And it’s a common finding during routine screenings that begin in your 40s. Roughly half of women over the age of 40 have dense breasts, according to the FDA.

A radiologist who reads your mammogram results will determine your breast density based on four categories:

  • Category A: The breasts are almost entirely fatty tissue.
  • Category B: There are a few areas of dense tissue scattered throughout.
  • Category C: There’s more dense tissue, and it’s spread evenly throughout.
  • Category D: The breasts are extremely dense.

If you fall into category A or B, you are not considered to have dense breasts.

Why do I need to know my breast density?

There are a few different reasons why breast density is important.

For starters, dense breast tissue can make it more difficult to detect cancer on a mammogram. Fibrous and glandular tissue appears white on a mammogram — but so does a possible tumor. “So [that] can make it harder for radiologists to visualize an abnormality,” says Tari A. King, M.D., chief of breast surgery at Dana-Farber/Brigham and Women’s Cancer Center in Boston.


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Beyond this masking effect, women with what King calls extremely dense breasts are at increased risk for breast cancer, though scientists are not sure why, the Centers for Disease Control and Prevention (CDC) notes.

What can you do if you have dense breasts?

So you just found out you have dense breasts: That doesn’t necessarily mean you need additional screening and added worry, King says. What it does mean is that you should have a conversation with your doctor, who will consider your overall breast cancer risk, and based on that risk, may recommend more imaging with an ultrasound or MRI.

When do you need a mammogram? ​

For individuals at average risk

  • Women ages 40 to 44 have the option to start screening every year.
  • Women 45 to 54 should get mammograms every year.
  • Women 55 and older can switch to a mammogram every other year, or they can choose to continue yearly mammograms.

According to American Cancer Society guidelines 

These tests do not have the same masking effects as a mammogram, but they may lead to more false positives and unnecessary biopsies and they can be more expensive, King says. For example, patients with Medicare Part B can expect to pay 20 percent coinsurance for a breast ultrasound if their doctor deems it necessary. People with Medicare Advantage plans may need pre-authorizations or other information from a provider to show an additional test is medically necessary.

“There’s not a one-size-fits-all approach when it comes to recommendations for additional imaging,” King says.

Having dense breasts is one risk factor on a list of several. Others include age (most breast cancers are diagnosed after the age of 50, the CDC says) and a family history of breast or ovarian cancer. Physical inactivity and alcohol use play a role in the risk, as well.

“We also know that postmenopausal weight gain is a very significant risk factor for breast cancer, and so women should be really counseled about maintaining the appropriate body weight as they go through menopause,” King says.

Knowing all your risk factors, including your breast density, “is a really important step forward for patients to be proactive” in their breast health care, Kalambo says.

Also important: Bringing any breast abnormality to your doctor’s attention, even if your mammogram or other imaging tests are clear.

“Mammograms are excellent tools, but they are not perfect, even in women who don’t have dense breasts. And so don’t take a negative mammogram as reassurance. If you are concerned about something, still bring that to your physician’s attention,” King says.

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