Breast Density

Breast density is a term that describes what your breasts are made of on the inside, as it appears on a mammogram. Breasts contain a mix of fatty tissue and firmer fibrous and glandular tissue. When there is relatively more of the firm, glandular tissue, the breasts are described as dense. This is simply a normal variation — many women have dense breasts, and it has nothing to do with how breasts look or feel from the outside.

Density is usually grouped into four categories, ranging from mostly fatty to extremely dense, and it is determined by a radiologist reading your mammogram, not by a physical exam. Several things can influence it, including age, genetics, and hormonal factors. Density often decreases as women get older, particularly after menopause, though this varies from person to person.

Breast Density matters for two reasons. First, dense tissue can make a mammogram harder to read, because both dense tissue and potential areas of concern appear white on the image, which can make a small finding harder to spot. Second, higher density is itself associated with a somewhat greater risk of breast cancer. For these reasons, women with dense breasts sometimes benefit from additional imaging, such as ultrasound or breast MRI, alongside their regular mammogram. Many regions now include density information in mammogram reports so that you are aware of yours.

Knowing your breast density helps you and your care team make the most informed choices about screening. Because dense tissue can hide small findings on a mammogram, being aware of your density opens a conversation about whether additional imaging might give a clearer picture in your particular case.

Density is not something to be alarmed by — it is common and normal — but it is useful information to have. Understanding that it can affect both how your mammogram is read and your overall risk lets you approach screening as an active participant rather than a passive one. With this knowledge, you can ask thoughtful questions and feel confident that your screening plan reflects your individual situation.