Under the new law, women with dense tissue will be told that while this is not abnormal, it can make detecting breast cancers more difficult and may be associated with an increased risk of cancer.
"This will help save women's lives," said Sen. John Flanagan (R-East Northport), who sponsored the bill. "The idea is to try to provide more information so that people can make better and more informed judgments about their personal health care."
Cancers that are diagnosed early can be easier to treat, according to the American Cancer Society.
Some members of the medical community have raised questions about whether the law would lead to unnecessary tests and cause undue anxiety.
"For some women, the density of their breasts is an indicator of risk of developing breast cancer, [but] for probably most women who have dense breasts, it is not an indicator of risk," said Dr. D. David Dershaw, a radiologist at Memorial Sloan-Kettering Cancer Center in Manhattan.
Dershaw said additional testing is a controversial topic. "The vast majority of those interventions do not discover a cancer," he said.
The American College of Radiology, a professional association, cautioned this year that there is no consensus about whether dense breast tissue warrants supplemental screening.
For Huntington resident and cancer survivor JoAnn Pushkin, the governor's signature felt like a victory after three years pushing for the law as the executive director of Are You Dense Advocacy.
Pushkin, 52, said doctors never told her she has dense breast tissue that could make cancer difficult to detect on mammograms. When she found a lump in 2005, an ultrasound revealed a tumor that had been growing for five years and hadn't shown up on mammograms, she said.
"I was denied the opportunity to advocate for myself because I was kept in the dark," said Pushkin, who has undergone multiple surgeries, and radiation and chemotherapy treatments. "Sometimes you don't know what you don't know."