Arecent study that questions the effectivenessof supplemental breast cancer screening for women with densebreasts couldbeona collision course with state laws mandating that women be notified if a mammogram shows they have high breast density. Experts say that about 40% to 50%of womenhavedensebreast tissue,whichhas been associated with higher breast cancer risk. Adding ultrasonography to mammography often is suggested because limited data indicate that it can strengthen breast cancer detection rates. Even so, uncertainty has surrounded whether the additional screening improves long-term outcomes and whether it’s cost-effective. But data published late last year show that supplemental ultrasonography produces only small health benefits while it substantially increases costs (Sprague BL et al. Ann Intern Med. doi:10.7326/M14-0692 [published online December 9, 2014]). Breast tissue is considered “dense” if it has excess fibrous or glandular tissue, according to the American College of Radiology. Some estimates have suggested that mammographic density accounts for 16% of all breast cancers (Assi V et al. Nat Rev Clin Oncol. 2012;9[1]:33-40). Consequently, these types of data helped build momentum for laws that require notification of women with dense breasts, largely led by a grassroots movement called “Are You Dense?” Women Need Information Nancy M. Cappello, PhD, has been a key force behind the state-by-state legislation for breast density notification. She has written about her personal experience, which began when her own mammogram was reported as being normal (Cappello NM. J Am Coll Radiol. 2013;10[12]:903908). Only 2 months later, however, she was diagnosed with stage IIIC breast cancer. As she wrote in the article, “My radiologist knew that I had dense breasts. My doctor knew that I had dense breasts. The only person who did not know was me: the woman with the dense breasts.” In fact, according to data published on the “Are You Dense?” website, 95% of women do not know their breast density (http:// www.areyoudense.org/). Fewer than 1 in 10 women learn about their dense breast tissue from their own physicians. In2009,Connecticutwas the first state to implement a breast density notification law requiring women to be notified after a mammogram showed they had high breast density. Since then, 19 other states have joined the movement by enacting laws of their own, with Ohio joining the roll in December 2014. Nearly a dozen additional statesareconsideringsimilar legislation,with only minor differences among the laws of participating states. Federal legislation also is on the drawing board in Congress—the so-called Breast Density and Mammography Reporting Act of 2015. The act would require that a mammography report summary be delivered to patients indicating their breast density according to standardized density measurements used throughout the United States.