A bill authored by state Sen. Joe Simitian, D-Palo Alto, that would require physicians to notify women who have dense breast tissue of their increased risk of breast cancer has been signed over the weekend by Gov. Jerry Brown and is now law of the land.

Senate Bill 1538 was proposed by Simitian a year after Brown had vetoed a similar proposal. The new bill requires women who get mammograms to get informed if they have dense breast tissue; that breast tissue can make it harder to evaluate a mammogram's results; that it is associated with an increased risk of breast cancer; and that a range of screening options are available.

According to Simitian, about 40 percent of the women who have mammograms have dense breast tissue, which appears on a mammogram and is thus difficult to distinguish from cancer. Simitian cited a January 2011 study by the Mayo Clinic that found that in women with dense breast tissue, 75 percent cancer is missed by mammograms alone.

"This is a life saver," Simitian said in a statement. "I'm tremendously thankful for the Governor's support of this measure, and for his willingness to listen to and work with us on this issue over the past year."

The legislation was proposed as part of Simitian's annual "There Oughta Be a Law" contest by Amy Colton, a Santa Cruz resident, registered nurse and cancer survivor. Despite undergoing routine mammograms, she had not been informed of her breast density until after she completed her treatment for breast cancer.

"I'm thrilled that the Legislature and the Governor have recognized the importance of SB 1538 to the women of California," Colton said in a statement. "This new law will provide women with important information about their physiology; and with that information they can be better advocates for their own health."