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Breast Density and Your Mammogram Report

Written July 2015

©2015, American Cancer Society, Inc. No.004802 - Rev. 7/15

Regular mammograms are the best way to find breast cancer early. But if your mammogram report said that you had dense breast tissue, you may be wondering what that means.


What is dense breast tissue?


Breasts are made up of lobules, ducts, and fatty and fibrous connective tissue.

• Lobules produce milk and are often called “glandular tissue.”

• Ducts are the tiny tubes that carry milk from the lobules to the nipple.

• Fibrous tissue and fat give breasts their size and shape and hold the

other tissues in place.


Your breasts will be seen as dense if you have a lot of fibrous or glandular tissue and not much fat in the breasts. Some women have more dense breast tissue than others. For most women, breasts become less dense with age. But in some women, there’s little change. Breast density is very common, and is not abnormal.

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How do I know if I have dense breasts?


Breast density is seen only on mammograms. Some women think that because their breasts are firm, they are dense. But breast density isn’t based on how your breasts feel. It’s not related to breast size or firmness.


Radiologists are the doctors who “read” x-rays like mammograms. They check your mammogram for abnormal areas, and also look at breast density. There are 4 categories of breast density. They go from almost all fatty tissue to extremely dense tissue with very little fat. The radiologist decides which of the 4 categories best describes how dense your breasts are.

Some mammogram reports sent to women mention breast density. At one time, doctors assigned a number to the density category, but it’s now worded in a way that’s easier to understand. Women whose mammograms show anything more than scattered areas of dense tissue may be told that they have “dense breasts.”


Breasts are almost all fatty tissue. There are scattered areas of dense More of the breast is made of dense glandular and fibrous tissue. glandular and fibrous tissue. This

can make it hard to see small tumors in or around the dense tissue.


Breasts are extremely dense, which makes it hard to see tumors in the tissue.