Medically Reviewed by W. Shawn Conwell, MD, FACR

Breast tissue density is essentially an observation of how much fat versus normal tissue (technically fibro-glandular tissue) comprises the breast. Fat appears black on a mammogram, while normal tissue appears white. Most forms of breast cancers are also white on a mammogram.

If your breast is composed almost entirely of fat (black) and a white cancer shows up, it’s very easy to see on a mammogram – kind of like a star in the night sky.

“If your breasts are dense, the mammogram displays lots of white (tissue) and no black (the fat),” says McLeod Radiologist W. Shawn Conwell, MD. “Finding a cancer in this circumstance is like searching for a polar bear in a snowstorm. It’s extremely difficult to see a cancer in dense breasts. Some 50% of cancers in extremely dense breasts are completely invisible on a mammogram.

Breast tissue falls into four categories – from almost entirely fatty to extremely dense:

1. The breasts are almost entirely fatty.
2. There are scattered areas of normal fibro-glandular densities.
3. The breasts are dense with fat mixed with regular tissue, which may obscure small masses.
4. The breasts are extremely dense, which decreases the ability of the mammogram to detect cancer.

Approximately 40% of the screening-age population, age 40 and older, has dense breast tissue (categories c and d above).

A RISK FACTOR
Dense breast tissue ranks as a potential risk factor for developing breast cancer, similar to a  having a first-degree relative (mother, sister) with breast cancer. However, this remains an area of active research.

MAMMOGRAMS & DENSE BREASTS
A mammogram remains the only technique to accurately determine dense breast tissue. Younger women tend to have denser breasts, but there are many older women who also have this composition.  Similarly, some young women have more fatty breasts. Density is not related to breast size, shape, or texture. You must have a mammogram to know if you have dense breasts.

ADDING ULTRASOUND, 3D
Radiologists have long been aware that mammography is not optimally suited for imaging dense breasts. Recent research, however, has established the ability of breast ultrasound, when used as a supplement to screening mammography in women with dense breasts, to increase cancer detection rates by nearly 60%.

In addition to breast ultrasound, using breast tomography (3D mammography) improves cancer detection rates in all women, including those with dense breasts.  The use of breast tomography also reduces unnecessary call-back examinations, shrinking by 50% the false positive rate of screening mammograms.

HOPE’S LAW
Enacted in 2016, Hope’s Law added South Carolina to 35 other states requiring breast tissue density notification to patients. Federal law requires mammography providers to notify patients directly, not just through their doctor, of the results of their mammogram.

The American College of Radiology and collaboratively produced with the Society of Breast Imaging can be found at www.mammographysaveslives.org by clicking on “Tools and Resources.”

Additionally, more comprehensive information can be found at www.densebreast-info.org.

If you have any further questions about these services, call the McLeod Breast Health Nurse Navigator at (843) 777-5418.

Have another question? Ask a Cancer Specialist.

To schedule your 3D mammogram at McLeod Health in Florence, Cheraw, Clarendon, Dillon, Loris or North Myrtle Beach, call (843) 777-2095 or click here.

Sources include: McLeod Health, American College of Radiology, American Cancer Society, Society of Breast Imaging