World Dense Breast Day: what your mammogram density notice means

Today is World Dense Breast Day, observed on the last Wednesday in September. It comes right before Breast Cancer Awareness Month begins tomorrow, and it focuses on a line in mammogram results that many people read without knowing what it means.

Breast tissue is made up of fatty tissue and dense tissue. Since September 10, 2024, a federal FDA rule has required every mammography facility in the United States to tell patients their breast density. Radiologists use four categories, from almost entirely fatty to extremely dense. If your tissue is dense, the required notice says that dense tissue makes it harder to find breast cancer on a mammogram and also raises the risk of developing breast cancer.

Dense breasts are common and are not a disease. The notice is meant to start a conversation. The FDA language advises patients to talk to their healthcare provider about breast density, their risk for breast cancer and their individual situation. For some people, that conversation leads to supplemental screening such as ultrasound or MRI in addition to the mammogram.

Many states also have their own density notification laws, so the wording you see may vary. Coverage for extra imaging also varies by plan, which is worth asking about before you book.

If you have had a mammogram, find your most recent results letter or patient portal report and look for the density category. If it says dense, write down one question for your next appointment. Your doctor is the right person to help you decide what fits your situation.