Breast Density Notification Law Takes Effect in California

The following article was written by Elissa Price, M.D., a specialist in breast imaging at UCSF Medical Center at Mount Zion.

Laws requiring that women be notified of their mammographic breast density now exist in six states.  In California this law took effect on April 1, 2013.  From that date forward, whenever a radiologist interprets a mammogram and reports that a woman has dense breasts, the woman must receive a letter from the imaging facility explaining that her breast tissue is dense. This information should then be discussed with the woman’s doctor.

Women who receive this notification should consider four important issues:

1)     The definition of breast density on mammography

2)     The impact of dense tissue on the radiologist’s ability to identify breast cancer

3)     The risk of breast cancer due to dense breast tissue

4)     The potential need for testing in addition to mammography

In a general sense, the breast is composed of fatty tissues and glandular tissues.  On a mammogram fatty tissue is dark and glandular tissues are white. The radiologist who interprets the mammogram judges breast density by how much glandular tissue is present, and categorizes the density according to the Breast Imaging Reporting and Data System (BI-RADS), a quality assurance tool published by the American College of Radiology. The new legislation requires that women be notified when the breast density judgment falls into the two highest of four categories established by BI-RADS.

While glandular tissue appears white on mammography, so does breast cancer.  Therefore, it can be more difficult to identify a cancer on a mammogram with more glandular tissue (that is, on a woman with dense breasts.) This phenomenon is known as “masking” because a cancer can be completely hidden, or “masked,” by the dense tissue.  Research has found that masking can decrease a radiologist’s ability to find a cancer by up to 20 percent.

Although breast density is a risk factor for breast cancer, we do not believe it is a strong risk factor. For women who are otherwise at low risk for breast cancer, dense tissue likely plays a limited role.

The need for additional screening after mammography in women with dense breasts is highly controversial. At UCSF we support a risk-based approach. If a woman with dense breasts desires additional testing, she should discuss this with her referring doctor. The doctor can discuss her breast cancer risks in more detail, and, if needed, the woman may choose to meet with a genetic counselor. Women who are found to be at high risk for breast cancer would likely benefit from additional screening, particularly breast MRI.

Several UCSF breast radiologists are key members of the California Breast Density Information Group (CBDIG), a statewide collaboration that offers more information about these issues for women and referring doctors.