WHAT ARE DENSE BREASTS?
Dense breasts refers to the amount of glandular tissue vs fat. The less fat (and the more glandular) makes the breast more dense. On a mammogram, which is a black and white and shades of grey, dense breasts appear "white" and fatty breasts appear more "dark.". This is important because cancers on a mammogram are also white and so it is more difficult to find cancers in women with dense breasts. In fact the more dense a breast, the more likely a mammogram will fail to detect a small cancer. In women with densest breasts a screening mammograms will miss 60% of breast cancer. Fortunately, on ultrasound cancers are dark. So it is easier to find a cancer on ultrasound in a woman who has dense breasts. In fact screening breast ultrasound will find 40% more cancers in women with dense breasts than mammograms will. On the other hand fatty (non-dense breasts) are predominantly black on a mammogram. Therefore cancers are more easily seen in women with fatty and screening ultrasound is not necessary.
WHAT IS THE DIFFERENCE BETWEEN A "SCREENING" AND A "DIAGNOSTIC" BREAST ULTRASOUND?
A screening breast ultrasound is done in an asymptomatic patient who has a normal breast physical examination and a normal mammogram. It is meant to screen for breast cancer. A diagnostic (or targeted) breast ultrasound is done to evaluate a palable mass or an abnormality seen on a mammogram.
WHO HAS DENSE BREASTS?
Two thirds (66%) of premenopausal women and 25% of post-menopausal women have breasts dense enough that a mammogram will miss their breast cancer
WHY IS IT IMPORTANT TO KNOW YOUR BREAST DENSITY?
As described, in women with dense breast, mammograms will miss a large percent of small potentially curable cancers. It has also been shown that dense breasts, increases the risk for breast cancer. Therefore women with dense breasts even if there s no family history of breast cancer should consider having a screening breast ultrasound at the time of their mammogram.