When breasts are made up of more fibroglandular tissue than fatty tissue, they are considered dense. Having dense breast tissue is usually inherited, but young age, weight loss with a reduction in body mass index or receiving hormone therapy can also influence your breast tissue. Breast density is classified into four categories. When you get a mammogram, the radiologist who interprets your images can determine if you have dense breasts and which category you match. Your breast tissue can be:

  • Almost entirely fat
  • Scattered fibroglandular
  • Heterogeneously dense
  • Extremely dense

If your mammogram reading falls within one of the last two categories, you have dense breasts. About 40% of screening-age women (40 and older) fall into the heterogeneously dense category and 10% fall into the extremely dense category, so a mammogram reading that depicts dense breasts is a common finding.

What does this mean for you?

It is important for women to know the implications of having dense breasts. As of April 2018, Wisconsin legislation began requiring mammography facilities to notify patients if they have dense breasts.

Having dense breast tissue in itself is not a cause for panic. According to Shadie Majidi, MD, a radiologist and section chief of Breast Imaging for the Froedtert & the Medical College of Wisconsin health network, “dense breast tissue alone minimally increases the chance of developing breast cancer. Other risk factors like family history are even more important considerations. Fortunately, we can calculate these and other risk factors with various risk assessment tools making it possible for you and your provider to remain proactive about your breast health.”

Dense breast tissue can have an impact on the ability to detect cancer on a mammogram. Because dense breast tissue and tumors both appear white on a traditional 2D mammogram, it can be difficult to differentiate between the two and see potential abnormalities. The more dense the breast tissue, the higher the likelihood that cancer can be hidden. That being said, annual screening mammography starting at age 40 has been shown to reduce deaths from breast cancer even in women with dense breasts.

Additional Screening Options

Since dense breasts make it harder to detect breast cancer with a mammogram, supplemental screening exams can be considered. The following three types of supplemental screening exams allow radiologists a deeper look at dense breast tissue to more accurately determine the possibility of underlying cancer:

  • Tomosynthesis – Also known as 3D mammography, this technology takes multiple low-dose image “slices” of the breast, reducing overlap of dense breast tissue and giving a more clear image. All women, especially those with dense breasts, may benefit from 3D mammograms, as they detect up to 40% more cancer than 2D mammograms and can reduce the callback rate for additional images by 40%. Tomosynthesis is offered at all Froedtert & the Medical College of Wisconsin health network sites that offer mammograms.
  • Ultrasound screening exam – At Froedtert & MCW Froedtert Hospital, automated breast ultrasound (ABUS) uses ultrasound technology to detect breast cancer in dense breast tissue. With ABUS screening images, dense breast tissue appears white, but unlike regular mammogram images, cancer appears grey. This technology allows breast tissue to be looked at in a different way and allows detection of abnormalities obscured by dense breast tissue on a mammogram. However, ABUS should not be a replacement for mammography and should be used in addition to mammography.
  • Breast MRI – A breast MRI with IV contrast, when combined with a mammogram, is the test of choice for women who have dense breasts and are at high risk of developing breast cancer. The American College of Radiology defines high-risk women as those with certain genetic mutations, history of chest radiation therapy, personal history of breast cancer or a calculated lifetime risk of 20% or more by a risk assessment model. The higher cost and sometimes limited availability of MRI requires appropriate use of this supplemental imaging modality.

Insurance coverage for these additional screening options varies, so contact your insurance provider.

Who reads your mammogram? It matters.

The Froedtert & MCW health network offers 13 locations throughout southeastern Wisconsin for breast cancer screening. In addition, six locations offer same-day results for diagnostic breast imaging, including Froedtert Hospital, Community Memorial Hospital, St. Joseph’s Hospital, Drexel Town Square Health Center, Mequon Health Center and CDI Westbrook Health Center. At these locations, every woman’s imaging results are interpreted by highly trained breast imaging radiologists. These specialists interpret thousands of mammograms each year and have the expertise to detect very subtle changes in breast tissue.

“Women need to know how important it is to have a breast-focused radiologist interpret their mammogram,” Dr. Majidi said. “It can make a big difference in detecting cancer as early as possible, and we know that early detection of breast cancer can save lives.”

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