Dense Breast Tissue

Breast density refers to the amount of dense breast tissue relative to fat in your breasts. Dense breast tissue is the normal supportive fibers and gland tissue in the breast. The amount of breast tissue can only be measured on a mammogram and is not related to breast size or firmness.

Breast density is important for two reasons:

  • Breast cancer can be harder to detect through mammogram on dense breast tissue.
  • Women who have more dense breast tissue have a slightly higher risk of developing breast cancer.

Breast density can only be determined by a mammogram, not by physical examination. Your official mammogram report from your screening mammogram will include your breast density category. If you have dense breast tissue, you will be notified of this in the result letter you receive.

Breast density types are separated into four categories:

  • A: Almost entirely fatty tissue (least dense)
  • B: Scattered amounts of breast tissue (uneven density)
  • C: Heterogeneously dense (the same amount of density throughout)
  • D: Extremely dense

Women with breast density scores of C and D are considered to have “dense breasts” and may benefit from further screening tests.