Since September 2024, every woman who gets a mammogram in the United States receives the same piece of information she may not have gotten before. Federal rules now require that the results letter state whether her breast tissue is dense or not dense.
About half of American women over 40 fall into the dense category, and it is not a disease or an abnormality. It describes the proportion of fibrous and glandular tissue to fat. It also tends to run higher in younger women and can change over time.
The reason it appears in the letter comes down to color. On a mammogram, fatty tissue reads as dark and is easy to see through. Dense tissue reads as white. So do tumors. According to the National Cancer Institute, that overlap makes mammograms less sensitive in women with dense breasts, meaning cancer is more likely to be missed. Dense tissue is also, separately, a risk factor for developing breast cancer.
There is a detail worth knowing about the letter itself. Radiologists sort density into four categories, but the patient notification only says dense or not dense. The specific category goes to the referring provider. A woman who wants to know whether she is at the high end has to ask for it.
The rule stops there on purpose. It tells women that additional imaging helps some people with dense tissue, then directs them to their own provider.
Rick Good spent ten years in the newspaper business, including with The News & Observer (Raleigh, NC) and The Greenville News (Greenville, SC). He co-wrote, with Melinda Coleman, Rutledge to Riley: Governors of South Carolina, 1776–Present (Published by The Greenville News), and is the author of Mind Games Trivia #1 (Amazon). He has recently spent 15 years creating original trivia content through Sounds Good Mobile Entertainment and continues that with his new company, SGME Software. He edits The Smart Reader’s money, real estate, and business coverage.
