Dense Breasts

This information explains the term "dense" breast on the mammogram. North Mississippi Health Services radiologists describe a mammogram as having a dense pattern if they see more white than gray on the mammogram. The reason this is important is that lumps are more difficult to see on a dense (white) mammogram. Radiologists may request staff to perform an ultrasound for women with dense pattern mammograms. The second test provides increased sensitivity for comparison with the mammogram. The following questions are frequently asked by patients.

Am I abnormal if I have dense breasts?

No. Breast density is an individual characteristic just like hair color or height. Young women tend to have dense breasts, although 25 percent of them do not. Older women tend to have more fatty, or low-density mammograms, but 25 percent of older women will have extremely dense breasts. Women often convert from dense to intermediate to low density during the course of their lifetime, but changes occur at different times for each woman. Breast density reflects the amount of fibroglandular tissue in the breast relative to the fatty tissue. Also, the amount of fluid retention in your breast at the time of the mammogram can affect the density. Density can change with pregnancy, lactation, menstrual cycle, weight loss/gain, hormone use, surgery, radiation therapy, and age. Having dense breasts does not mean you have fibrocystic disease.

Are my dense breasts caused by diet?

No. Your individual characteristics and hormonal status can affect your breast density. Losing more than 20 pounds may increase your breast density, but individual items in your diet do not significantly affect breast density.

If the mammogram is less sensitive for dense breasts, do I still need yearly mammograms?

Yes. Although the mammogram of a dense breast may not show lumps as clearly as the ultrasound, it is still the best way to look for microcalcifications. Most microcalcifications are part of normal aging in the breast. If microcalcifications are present in a tumor, they can be the smallest, earliest sign of some cancers. Fortunately, microcalcifications show up on mammograms better than on any other test available today, regardless of how dense the breast is. For that reason, yearly mammograms are still recommended in women age 40 and over and, in certain situations, in younger women.

Is it dangerous to have dense breasts?

No. Having dense breasts does not mean you are at a higher risk than anyone else of developing breast cancer. If you have dense breasts, however, you have a higher chance of a lump not showing up on your mammogram. This can be compensated for by a thorough breast examination and breast ultrasound. The ultrasound detects lumps hidden by overlapping normal breast tissue on the mammogram. It does this in two ways. First, it shows the breast in a straight line from the skin to the chest wall with no interference from what might be on top of or next to an area of interest. The mammogram is a composite picture, with overlap from side-to-side to top-to-bottom, but the ultrasound shows us a cross-section with no overlap. Also, the ultrasound looks at a different physical property of tissue: its fluid content, not how x-rays pass through tissue. Fluid-filled structures show up darker than surrounding tissue on ultrasound, instead of the same shade of white as the surrounding tissue on a mammogram.

What if my doctor feels a lump and it doesn't show up on the mammogram?

This is not a rare situation. Ultrasound is an excellent way to check if a physical finding is not showing up on the mammogram because it is part of a normal lumpy breast tissue or because it is hidden by dense breast tissue. Ultrasound detects abnormalities by difference in fluid content because it is extremely sensitive to fluid. Ultrasound routinely shows cysts that don't show up on mammograms. Ultrasound also often shows solid (not fluid-filled) lumps that don't show up in mammograms of dense breasts. The ultrasound characteristics of these solid lumps have been shown to be very accurate in predicting which lumps are suspicious in certain situations. The imaging of solid lumps is still slightly less reliable than that of cysts, and additional follow-up or biopsy is sometimes necessary. If the ultrasound doesn't show a cyst or a solid mass, it often shows which anatomical feature of normal breast tissue is causing the lump that is felt. Ultrasound is extremely reliable in this situation as well, as long as it is performed by an experienced specialist, such as those at North Mississippi Health Services locations offering this service. 

Can ultrasound tell the difference between cancer and a non-cancerous cyst?

Yes. Cysts are non-cancerous fluid collections, and ultrasound is exquisitely sensitive to their presence. It can show cysts as small as 2 mm, the size of this letter "o." Not only does the ultrasound show tiny cysts hidden on the mammogram, but it even shows the cyst wall and cyst contents with enough detail for the physician to decide whether a cyst needs to be aspirated (drained with a needle) for further testing. The features of a simple cyst (smooth walls, completely liquid content, acceleration of the sound beam) are completely different from those of cancer (irregular walls, mixed content, interruption of the sound beam) and easily recognized by an experienced breast ultrasonographer. Ultrasound plays a major role in evaluating dense breasts. Many other technologies are currently being investigated to see whether they can play a role in further evaluating dense breasts, but at this time their value remains unproven.

We hope this removes some of the mystery associated with the term "dense breast." If you should have any further questions, please contact one of the breast imaging professionals at one of our locations.

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