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Dense Breasts Explained

1. The medical term dense breast refers to a woman who has breast tissue that is not composed of very much fat between the glands and ducts of the milk system so that the tissue is litteral thicker and less visible on x-rays such as mammograms.

2. Your gyno can detect breast density on exam, but the formal definition of dense breasts is based on your radiologist grading this on exam.

3. It is only relatively recently that women were informed of the density findings on their mammogram. Mammographic breast density is also now graded along with the other characteristics of your breast reported on a mammogram.

4. Dense breasts are important to know about. 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.

5. Women who are heavier tend to have more dense breasts, like other features of our breast the density is somewhat genetic. Asian women have denser breasts, yet less breast cancer!

6.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 potentially affect the diagnostic interpretation of mammograms.

7. Your density on your mammograms can change with many factors besides 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, and advocate for those with dense breasts to be sure to stick with yearly mammograms. There may be ways your physician can advise you as to how to reduce your breast density.

8. The grading of breast density is not taken as an isolated finding, but in context of what else is going on in the breast tissue. 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.

9. 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!

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.


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