What is Breast Density and what does it mean?

Breast density is a way to describe the types of tissue that make up the breast. The breast is made up of glandular or ductal tissue, fibrous connective tissue and fatty tissue.  The amount of each of these tissues varies in women. Women who have more fibrous connective and glandular tissue than fatty tissue have more breast density. Breast density can make breast cancer difficult for a radiologist to see on a mammogram.

Mammogram of BI-RADS III Heterogeneously Dense Breasts

Breast density changes over a woman's lifespan, usually decreasing with age, but a certain proportion of women have dense breast tissue that remains extremely dense throughout life. Other factors which can affect breast density are relative body mass index, age at first childbirth, postmenopausal hormone replacement use and/or genetic make-up. Regardless of breast size or shape, women with dense breasts have a substantially higher risk of breast cancer than women whose breasts are classified as "fatty". 

Breast Density: How do you know?
Only your doctor can determine your individual breast density from a mammogram. Ask your doctor about your breast density assessment and individual breast cancer risk factors after your next mammogram.

What's your BI-RADS?
Breast density is classified using the BI-RADS (American College of Radiology Breast Imaging Reporting and Data System) scoring method. This method describes four different categories:

BI-RADS I - Entirely fat
BI-RADS II - Scattered fibroglandular densities
BI-RADS III - Heterogeneously dense
BI-RADS IV - Extremely dense

The BI-RADS classifications are routinely used as a part of a radiologist's mammographic assessment and are available for women who get yearly mammograms. Ask your doctor; every woman should know her BI-RADS breast density class.