Breast Density Legislation and Clinical Evidence.

Breast density inform legislation is widely accepted in the United States and has fueled research regarding the clinical significance of dense breast tissue present on mammography and the value of supplemental screening. This article reviews the origins and current status of breast density inform laws and strategies for optimal breast density determination. Clinical evidence that dense breast tissue is associated with increased breast cancer risk is presented, together with a review of relative risk compared with other risk factors. Finally, there is in-depth analysis regarding the rationale, benefits, and risks of supplemental screening modalities, including ultrasound, tomosynthesis, and MRI.