More information about density reported on your mammogram can be found below:
Mammographic breast density because of these risk factors is also now graded along with the other characteristics of your breast reported on a mammogram.Women with dense breast tissue have 3-5 times greater risk of breast cancer than women with normal breasts, and hormone therapy can increase breast density in 30-50% of women who take it. The National Cancer Institute Breast Cancer Surveillance site also has a lot of data on breast density at their site. They have developed a tool for health care providers to help them understand what patients are at most risk from dense breasts. Generally a physician can look at the mammogram and the amount of ‘black’ verses ‘white’ components of the x-ray. Very white means very dense. Since breast tissue is actually 3 dimensional the denseness of the breast also is based on the internal structures that the radiologist is seeing. The thought has been that too dense of a breast would then obscure the view of a cancer. In general the pictures are graded by the ‘percentage’ of density, and greater than or equal to 75% dense correlates with dense breasts and less ability to predict the presence of a very small cancer. For decades the individual reading a mammogram reported their interpretation of density, but now the CAD or Computer Aided Detection programs can very accurately report the percent of density. Women who are heavier tend to have more dense breasts, like other features of our breast the density is somewhat genetic. Density is also related to hormone use and thus it is the position of the North American Menopause Society that taking estrogen and progesterone hormone therapy will hare the diagnostic interpretation of mammograms. Your density on your mammograms will change with many factors besides whether you have a Western or a Mediterranean diet and hormone use. Having a baby decreases density, and having too much alcohol increases density. Aging and decreasing hormones will change your density the most dramatically and decrease its density. And the more your density decreases the less your risk for breast cancer over time. USPSTF considered whether women with dense breasts need extra mammograms and generally found that wouldn't be so helpful. Other women's advocacy groups may not agree. There may be ways your physician can advise you as to how to reduce your breast density. So next time you are discussing your mammogram report with your gyno, ask if your breasts are less or more dense than the last picture you had taken!