Closeup of the chest of a woman wearing a bra, and of a woman not wearing a bra, with an inset showing the mammograms of breasts that are fatty and dense.

Breast Density

Many women have breasts that are dense as opposed to being fatty. (Breasts that are not dense are called fatty.) While it is impossible to tell if a woman’s breasts are dense by feeling them, it is very important for women to know if their breasts are dense. That’s because it is difficult to spot cancer in routine mammograms when a woman has dense breasts (see the mammograms below).

These mammograms show the differences in how fatty and dense breasts look on a mammogram, and the challenge of spotting breast cancer in dense breasts.

Mammograms showing how easy it is to detect cancer in a fatty breast as opposed to a dense breast.
Four different breasts, with the question of "can you spot the tumors on these mammograms?"

Three excellent websites for women about dense breasts:

Mammograms are less effective for women with dense breast tissue. Medical experts disagree on what to do about it from Stat News.

CDC Basic Info About Dense Breasts The website of the CDC.

Dense Breast Info by Dr. Wendy Berg and JoAnn Pushkin A leading website about dense breasts. The Story of A Woman whose Breast Cancer was missed on her mammograms over multiple years and on several consecutive screening mammograms.