Why Women Have Them and What to Know

If you’ve ever had a mammogram, you may have noticed a note on your results about your breast density. Maybe your natural breast tissue is not dense or all, extremely dense or somewhere in the middle. If you do have what’s known as “dense breasts,” your OB/GYN most likely brought it to your attention. If not, be sure to ask. Knowing your breast density is important, as it can impact certain health screenings like mammograms.

It may sound scary, but rest assured that nearly half of the female population has this type of breast tissue. “According to the American College of Radiology, approximately 40 to 50 percent of women ages 40 to 74 have dense breasts,” says Washington, D.C. OB/GYN Stephanie Hack, MD. Here, we break down what dense breasts are, why some women have them and what to know if you do.

Featured Experts

• Angela Wilson, MD, an OB/GYN at Montefiore Einstein Advanced Care in New York
• Stephanie Hack, MD, an OB/GYN based in Washington, D.C. and founder of Lady Parts Doctor, a women’s health platform
• B. Aviva Preminger, MD, a board-certified plastic surgeon based in New York

What Are Dense Breasts?

According to Dr. Hack, the term “dense breasts” refer to breasts that have a higher proportion of fibrous and glandular tissue compared to fatty tissue. “When we speak about dense breast tissue, we are speaking about a radiological finding on a mammogram,” says New York OB/GYN Angela Wilson, MD. “It does not correlate to any finding on a physical exam, such as breast size or firmness.” On a mammogram, or X-ray image of the breasts, dense tissue appears white and fat tissue looks black. “The more opaque, or white, tissue, the more dense the breasts appear on the mammogram,” Dr. Wilson adds.

These are the four categories for breast density according to the American College of Radiology’s Breast Imaging Reporting and Data System:

• A: Almost entirely fatty. The breasts are almost entirely made up of fatty tissue. There is very little dense breast tissue.
• B: Scattered areas of fibroglandular density. The breasts are mostly made up of fatty tissue, but there are some scattered areas of dense breast tissue.
• C: Heterogeneously dense. Most of the breast tissue is dense, but there are some areas of fatty tissue.
• D: Extremely dense. Nearly all of the breast tissue is dense breast tissue. There is very little fatty tissue.

Are Dense Breasts Hereditary?

While Dr. Hack says we don’t fully understand the exact reasons why some women have dense breasts, we know several factors can influence breast density, including genetics. “Women with dense breasts often have family members with the same condition, indicating that genetics play a role,” says Dr. Hack. Age is also a factor. “There is more glandular and fibrous tissue in younger women, therefore contributing to a higher density,” Dr. Wilson explains. “As we age, and with changes in hormonal status, this tissue decreases and is replaced with more fat tissue, making the tissue less dense.”

Of course hormones have an impact as well, as they do with so many other components of our health. “Hormonal changes, including those during pregnancy, menopause or hormone replacement therapy, can affect breast density,” Dr. Hack says. Dr. Wilson adds that breast density can also differ depending on your monthly hormonal cycle. “It can increase in the two weeks prior to the onset of menstruation.”

Do Dense Breasts Affect Mammograms, or Their Results? 

Dense breast tissue can make mammograms more difficult to interpret, says Dr. Hack. “Both dense tissue and tumors appear white on a mammogram, so the dense tissue can mask tumors, making them harder to detect. Women with dense breasts may require supplementary screening methods, such as breast ultrasound or MRI, to improve the detection of abnormalities.”

“Caring for your breasts is another important part of self-care,” Dr. Hack continues. “Stay informed about your breast density status and what it means for your screening routine. If you have dense breasts, make it a priority to schedule regular mammograms.” According to The American Cancer Society, women between the ages of 40 and 44 who are at average risk for breast cancer have the option to start screening with a mammogram every year. Additionally, women ages 45 to 54 should get mammograms every year. “Be proactive in discussing your breast density and any concerns you may have with your healthcare provider,” says Dr. Hack. “Many states mandate that women be informed if they have dense breasts following a mammogram. Use this information as a tool for self-advocacy. Finally, while you can’t change your breast density, you can adopt a healthy lifestyle to support overall breast health.”

Does Having Dense Breasts Increase Your Risk of Getting Breast Cancer?

Referencing the four categories of breast density detailed above, Dr. Wilson explains that “patients who fall in the two highest categories are at risk of having a mammogram miss a small mass. Also, the mammogram may be less sensitive in detecting abnormalities. Women should know that having dense breasts does affect their risk for breast cancer in two ways. First, in that denser breast tissue decreases the sensitivity of mammograms in detecting small masses and developing breast cancers. The other way is that patients with dense tissue have an independently slight increase risk of breast cancer due to the fact that the majority of cancers develop in the glandular tissue.”

However, Dr. Wilson says that, thankfully, this does not translate to an increased mortality from breast cancer. “Despite this increased risk, the American College of OB/GYN states that there is not enough clinical evidence to support routine use of supplemental screening modalities, such as breast ultrasound or MRI in these patients. Nevertheless, additional testing may be warranted in patients with other risk factors to further evaluate the breast tissue. Patients should speak to their providers about their specific risks to determine if any additional testing is warranted.”

Do Dense Breasts Impact Plastic Surgery Procedures?

You may be wondering if your dense breasts will negatively impact your breast augmentation with breast implants, or cause any unnecessary complications. However, implants are placed underneath the breast tissue, so the density of the breasts isn’t a concern. Having said that, New York plastic surgeon B. Aviva Preminger, MD, says dense breasts can sometimes make preoperative imaging more challenging. “Overall though, on a positive note, dense breast tissue tends to hold up better with time.”