Since September 2024, every U.S. mammogram report must tell patients whether their breast tissue is dense. Here is what that notice means, why it matters and what to ask your care team.
If you’ve had breast cancer and still get mammograms, your results letter now includes a sentence about breast density. Under a U.S. Food and Drug Administration (FDA) rule that took effect Sept. 10, 2024, every mammography facility must tell patients whether their breast tissue is dense. For many survivors, that line raises new questions about follow-up care. For Breast Cancer Awareness Month, here is what the notice means for people who have already been diagnosed.
The notice goes to anyone who has a mammogram, including people being monitored after treatment. That includes those who had a lumpectomy and those who had a mastectomy on one side and still get mammograms of the other breast. CURE
The letter will say either “Your breast tissue is not dense” or “Your breast tissue is dense.” Both versions explain that density can make cancer harder to see on a mammogram and is linked to a higher chance of developing breast cancer, and both encourage you to talk with your provider.
Breasts are made of fatty tissue and fibroglandular tissue (milk glands, ducts and supporting tissue). They are called dense when they have more fibroglandular tissue than fat. Density shows up only on a mammogram; it has nothing to do with how breasts look or feel. About half of U.S. women 40 and older have dense breasts, according to the National Cancer Institute (NCI). It is common and normal.
People who have had breast cancer already face a higher chance of a new cancer in either breast. Dense tissue adds two concerns. First, it can hide a tumor, because both look white on a mammogram. Second, density is itself linked to higher breast cancer risk, according to the Centers for Disease Control and Prevention (CDC).
There is also reassuring news. The CDC notes that people with breast cancer who have dense breasts are not more likely to die of it than those with fatty breasts.
This is the most important question to bring to your care team. The American College of Radiology (ACR) recommends adding an annual breast MRI to mammography for people with a personal history of breast cancer who have dense breasts, as well as for those diagnosed before age 50. Other options your team may consider include 3D mammography (digital breast tomosynthesis) or breast ultrasound, especially if MRI isn’t possible for you.
Not every guideline group agrees, and your oncologist will weigh your full picture, including the type of cancer you had, the treatment you received, your age at diagnosis, genetic test results and family history. Coverage also varies, so check with your insurance before scheduling extra imaging.
Density isn’t fixed. It tends to be higher in people who are younger or taking hormone replacement therapy, and some breast cancer treatments lower it. Tamoxifen, a hormone therapy used for hormone receptor-positive breast cancer, reduces breast density in many patients. Studies have found that patients whose density dropped substantially while taking tamoxifen had better long-term survival than those whose density stayed the same. This is not yet used to guide treatment decisions, but if your letter says your density has changed since starting hormone therapy, it is worth mentioning at your next appointment.
A dense-breast notice is not a new diagnosis and does not mean your cancer has come back. Keep up with your recommended surveillance, know how your breasts and chest area normally look and feel, and report changes such as a new lump, skin dimpling or nipple discharge, even if your last mammogram was normal. CURE has more on
