Radiologists are the doctors who determine whether a woman has dense breasts. They do so after looking closely at images from mammograms. Radiologists may also use computer software to measure breast density. Breast density cannot be determined by how a breast looks or feels.
There are 4 categories of breast density. Here is more to know about each category:
Category A. Fatty, or almost entirely fatty breasts. This means that most of the breast is made of fat tissue. On a mammogram, a fatty breast appears as mostly dark grey or black. While most of the breast is fatty tissue, there may be a small amount of dense (fibroglandular) tissue that looks light grey or white. About 10% of all women have fatty breasts. Breasts in Category A are not considered dense.
Category B. Scattered areas of fibroglandular density. The breast has a mix of fatty tissue which appears dark grey or black, and scattered dense (fibroglandular) tissue which looks light grey or white. It can be hard for radiologists to find cancer, which often also look light grey or white, in areas that are dense. About 40% of all women have this type of breast. Breasts in Category B are not considered dense.
Category C. Heterogeneously dense breasts. Large portions of the breast are made of dense (fibroglandular) tissue. On a mammogram, the breast appears mostly light grey or white. It is harder for radiologists to find cancer, which often also looks light grey or white. About 40% of all women have heterogeneously dense breasts. Breasts in Category C are considered dense.
Category D. Extremely dense breasts. Most of the breast is made of dense (fibroglandular) tissue. On a mammogram, the breast looks almost all white. This makes it very hard for radiologists to find cancer, which often also looks light grey or white. About 10% of all women have extremely dense breasts. Breasts in Category D are considered dense.
For more information, see Q+A “How do I find out my density category?”
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