This image shows a negative screening mammogram of 45-year-old woman with dense breast tissue.

Approximately one in eight women will develop invasive breast cancer during her lifetime, according to the American Cancer Society (ACS). In recognition of Breast Cancer Awareness Month, we are publishing a three-part Breast Imaging Series throughout October. Today’s post, the final in our series, discusses breast density.

Breasts contain fibrous, glandular, and fatty tissue. Generally, breasts are considered dense if they contain a lot of fibrous and glandular tissue and less fat. Breast density is classified on a mammogram report in one of four ways:

  • Almost entirely fatty
  • Scattered areas of fibroglandular density
  • Heterogenously dense
  • Extremely dense

According to the American College of Radiology, 80 percent of women in the United States fall into one of the middle two categories, 10 percent have almost entirely fatty breasts, and the remaining 10 percent have extremely dense breast tissue.

Breast density is important for several reasons. Dense breast tissue may increase a woman’s chance of developing breast cancer. Also, detection of breast cancer using mammography is more difficult in women with dense breast tissue. Read More »