Posted by: bcconnections | April 12, 2013

California’s Breast Density Law

Effective April 1, 2013, California State Law SB 1538 requires radiologists to inform women if they have dense breast tissue on screening mammography.  Under the new law, about 50% of women will receive the following statement with their mammogram results:

“Your mammogram shows that your breast tissue is dense. Dense breast tissue is common and is not abnormal. However, dense breast tissue can make it harder to evaluate the results of your mammogram and may also be associated with an increased risk of breast cancer.

This information about the results of your mammogram is given to you to raise your awareness and to inform your conversations with your doctor. Together, you can decide which screening options are right for you. A report of your results was sent to your physician.”

What does it mean to have dense breasts?

Breasts are composed of a mixture of fat, glandular tissue and fibrous tissue.  If breasts have little fat but a lot of glandular and fibrous tissue, they are considered dense.  Currently, breast density is qualitatively classified by radiologists into four categories:

  • Almost entirely fatty (10% of women)
  • Scattered areas of fibroglandular density (40% of women)
  • Heterogeneously dense breasts (40% of women)
  • Extremely dense breasts (10% of women)


Women with breasts categorized as heterogeneously dense and extremely dense are required, under the new law, to receive notification of this classification.

The implications of having dense breasts are two-fold.  First, the sensitivity of mammography is lower in dense breasts.  Cancer can be masked in dense breasts because both cancer and dense breast tissue appear white on a mammogram.  Second, women with dense breasts have an elevated risk of getting breast cancer.  If a woman has heterogeneously dense breasts, her risk is 1.2 times greater than a woman with average breast density, and if a woman has extremely dense breasts, her risk is 2 times greater.

Having dense breast tissue does not mean that a woman should stop getting yearly mammograms.  Instead, she should speak with her doctor about her risk factors and discuss whether other screening modalities would be appropriate complements to mammography.  These tests include breast MRI, breast ultrasound and 3D mammography.

Sources/More Information:


Stanford Breast Density

American College of Radiology

State Senator Joe Simitians’ website


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