As of January 1, 2015, a new Massachusetts law requires patients to be informed if they have dense breasts on routine screening mammograms.
Breast tissue is composed of fatty tissue (dark gray or black on a mammogram) and dense tissue (white on a mammogram). If the normal white breast tissue makes up a significant portion of the entire breast, the breast is classified as being dense. To understand what breast density means further, please visit Introduction to Breast Density.
Dense breast tissue is not abnormal. About half of all women undergoing screening mammography have dense breasts, and the majority of women under the age of 50 have dense breasts.
Some experts believe that having dense breasts may slightly increase the risk for breast cancer. This risk is believed to be small, and is one of many risk factors that may contribute to a woman’s overall risk for breast cancer. To understand how different risk factors affect your likelihood for developing breast cancer, please visit Understanding Cancer Risk.
Having dense breasts, however, can make it more difficult to detect signs of breast cancer on a mammogram because dense white normal breast tissue may hide an underlying cancer (that also looks white on a mammogram).
Although there is no perfect screening test for breast cancer, mammography continues to be the most important. Other methods of screening exist, such as breast ultrasound and MRI, but these tests are meant for women at high risk for developing cancer in their lifetime. At this time, there is not enough evidence to support additional forms of screening in low or average risk women. Also, additional screening tests (besides mammograms) may not be covered by health insurance. Patients with dense breasts may want to discuss their individual risk factors and the possibility of additional tests with their primary care providers. If performed, these additional screening tests should be obtained as supplements to mammography. They should not replace mammography.