Breast density refers to the ratio of fatty tissue to glandular tissue (milk ducts, milk glands and supportive tissue) on a mammogram. About 50% of all women (40% of mammography age) have increased density (“dense breasts”) as they have an increased amount of glandular tissue compared to fatty tissue. Younger women, premenopausal women and women using hormone replacement therapy are more likely to have dense breasts. Dense breasts are both an independent risk factor for the development of breast cancer and increase the likelihood that cancer will be missed by mammography. This is because breast cancers are more difficult to see on mammography in women with increased breast density.
In 2003, Nancy Cappello, Ph.D., was diagnosed with a stage III breast cancer only a short time after having a normal mammogram. She had dense breasts but did not know that it put her at higher risk for a cancer or that it could make a cancer more difficult to detect. She lobbied in her home state of Connecticut for insurance coverage for ultrasounds for dense breasts, and a law was enacted in 2005. She then worked towards another law, which went into effect in 2009, requiring women to be provided with general information about breast density. Other patient advocacy efforts followed. In 2013, New York became the first state to require that women be informed if their mammogram demonstrates that their breast tissue is “dense.” In 2014, both North Carolina and Pennsylvania enacted laws which require that women be provided with their actual mammographic breast density category (e.g. fatty, scattered fibroglandular density, heterogeneously dense, or extremely dense).
In 2010 patient advocate JoAnn Pushkin, who lobbied for New York State’s inform law, initiated efforts on both the federal legislative and regulatory levels for a national reporting standard. Federal breast density notification laws have been introduced but none have yet passed.
As of December 2018, there are 35 states with laws mandating that women be provided with some level of information about their mammographic breast density. Three additional states have efforts for density reporting or education but do not mandate notification. Only 7 states have laws requiring insurance coverage for additional imaging for women with dense breasts – though, generally, additional imaging will be covered (subject to copay/deductible) if ordered by a physician.
For an updated map indicating states with density notification laws, go to densebreast-info.org/legislation.aspx.
There are currently no national guidelines for additional screening of dense breasts.