Breast health

Dense breasts and “dense mammograms”

by Dixie Mills, MD, FACS

• What is dense breast tissue?
• Are dense breasts a risk factor for breast cancer?
• Alternative imaging for women with dense breasts
• How else can I create breast health?

By getting to “know” — and love! — their breasts, I think most women can become more comfortable with their bodies and inspired to take good care of themselves. As a breast health specialist, I meet many women who want and need better clarification of the language describing issues such as “dense breasts,” noted on their mammograms.

Just one of the many amazing features of a woman’s breast tissue is its characteristic density. Many women have shared with me how they were informed in the past of their “dense breasts,” but given little background as to what having dense breast tissue might mean for them. If you’ve been told your breasts are dense, you would probably like to be able to put this information into some context. Every woman should be told how dense her mammograms are. (I tell all my patients that they aren’t dense, just their mammograms!) Here are some thoughts for your consideration.

What is dense breast tissue?

Dense is usually a mathematical term meaning crowded or packed or a greater number of “things” in a certain volume. What this means on a mammogram is that there is a greater proportion of whiteness to grayness in the breast. (See image comparing breast tissue types). The whiteness on the mammogram is a combination of the glandular or ductal tissue of the breast and the fibrous supporting tissue. The grey is the fatty part of the breasts. As women age, their breasts on their mammograms get more grey (like their hair) because they don’t need the milk ducts anymore.

Genetic research in the past decade or so has revealed that dense breast tissue is mostly a heritable trait. But how your breasts feel doesn’t always correlate with how “dense” the tissue appears on imaging, so you won’t know you’ve inherited this feature until you get a mammogram.

There’s no universal measure that quantifies breast tissue density — at least, not yet. For a while now, readers of mammograms have most commonly expressed it as a percentage of the total breast area occupied by radiologically dense tissue. But some suggest it would be more helpful to keep track of both the total amount of dense tissue along with the percentage, because a woman’s breast density is indirectly related to her age, her body mass index, and some other breast cancer risk factors that may or may not change over time.

So for now, we don’t really have an ideal method for quantifying density, especially as it relates to what’s on the minds of women everywhere when they go for a mammogram — their risk for cancer.

Are dense breasts a risk factor for breast cancer?

Researchers have been studying this question for some time now. While the relationship between breast density and physiology is still not at all clear, this tissue characteristic does directly affect the likelihood of being able to detect a cancer with mammography, especially if you are under 50. Finding a cancer in dense breasts is something like tracking a polar bear or a white rabbit in a snowstorm. (I discuss some of the issues regarding imprecision and limitations of our current breast imaging technology in my article on mammograms.)

But apart from the challenge that breast density can pose for reading mammographic images, it is now looking like breast density is a true and significant risk factor — something I don’t like because my mammograms are dense, and it doesn’t seem like it should be a risk factor.

If your mammograms are dense, annual screening in your 40’s is probably going to be less helpful. Depending on your risk factors or personality, you may want to forego annual mammograms or perhaps go every two to three years until age 50, or pursue other means of screening. (See imaging alternative suggestions below for help in deciding what’s best for you.)

Can you make mammograms less dense? Unfortunately, there is no simple answer here. Aging helps some, as does childbearing. But if you want an immediate solution and you’re still menstruating, you can try having your mammogram right after your period, when your hormones are lower, although this can be somewhat difficult to schedule.

We also know that taking hormones tends to keep breast tissue dense. Some of the ways in which your body processes hormones and responds to changing hormones levels are linked to your genetic blueprint. But some are very much influenced by your everyday environment, too, including simple daily choices about diet, lifestyle, hormone replacement, and other variables that can support your hormonal balance.

For more on how the breast responds to changing hormones, see my articles on the beautiful lumpy breast, fibrocystic breast condition, the breast and estrogen controversy, and progesterone and the breast.

Suggestions about imaging for women with dense breasts

Understanding what a reading of “dense breasts” might mean for a woman may take a bit of detective work, however. Practitioners usually only receive the radiology report, not the images themselves — neither of which are always easy to interpret, even by the experts.

To offset some of the frustration of a dense mammogram reading, I do recommend that women have their mammograms taken consistently each time at the same accredited site. (It’s against the law to provide mammograms without being accredited, so it is rare that a center wouldn’t be.)

If practicable, women with family histories or other factors associated with an elevated risk of breast cancer should be screened at a breast center where they can be informed of their results the same day and have additional testing (if necessary), done at that same time or scheduled in a timely fashion. In an ideal world all women could have their testing done this way — what a lot of fear, loathing, and needless anxiety that would relieve! Unfortunately, the cost of this kind of practice can be prohibitive, and there are not enough dedicated mammographers (radiologists who specialize in the breast) to make it feasible for everyone.

Keep in mind that not all mammograms are taken or read using the same equipment or protocols. Imaging equipment and methods used to image women’s breasts can vary even within some centers, but I think it’s ideal for a woman who has dense breasts to have these variables be consistent, if possible. Ideally, the individual reading her mammograms might also become somewhat familiar with her tissue characteristics over the years.

Some are read once, some double-read, some are digitized, and some may use computer-aided detection software, but all are subject to human error. Sometimes the person reading them can be tired or less experienced. Fewer doctors are going into mammography now for fear of being sued over dubious results that come from the imperfect technology. For these reasons, getting a second opinion is always a good idea.

But there are screening and diagnostic breast imaging methods other than mammography now being developed and in limited but increasing use, that may be more appropriate for women with dense breasts.

Alternative imaging techniques for women with dense breasts

If your mammograms are dense, or you do not believe in or want to have a mammogram, you may want to request ultrasound screening. Ultrasound and mammography do not visualize tissue in an equivalent fashion, though, so one is not always better than the other as an imaging technique — only different. MRI (magnetic resonance imaging) is being intensely researched and fast becoming an important tool for women with a strong risk history, and breast thermography is another option. Not all centers will provide these services, and not all insurance policies cover them, at least not for screening purposes, so they can be expensive.

Some institutions are using digital mammography, where the pictures are stored on a computer, rather than film, and reviewed on a high-resolution monitor. The computer aids in analyzing the changes from year to year. Like all advanced technology, this equipment is upgraded frequently and is still very costly.

According to a study published in the New England Journal of Medicine, digital mammography offers significant benefits over film for premenopausal women and women with dense breasts. This is partly because digital image processing allows the degree of contrast in the image to be manipulated; it can be turned up in denser areas of the breast where the contrast is lowest. Even so, both groups were equally prone to giving false-positive results. Another benefit of digital mammography is that a radiologist can view your file from a remote location, which is good for second opinions!

Regardless, not all mammography centers have bought into the new technologies. But I am confident that with all the research and development taking place, we women with dense breasts and dense mammograms will have better and better options in the future.

To learn more about breast screening guidelines, see my article on mammograms — deciding what’s right for you.

How else can I create breast health?

Healthy breasts are part of healthy bodies so what you do for your body — eat well, exercise, sleep enough — is also improving your breast health. Don’t let the notion of having dense breasts hex you but be aware that you may have to take a bit extra care of your breasts. My breasts are not lumpy anymore so I regularly just check them out. Dense breasts on mammograms does not necessarily mean that one has difficult breasts to examine. I’ve come to think of the whiteness or density on my mammograms as a benevolent good white light shining onward — not really sure how it helps but it doesn’t hurt!

Related to this article:

References & further reading on on dense breasts and dense mammograms

 

Last Modified: 09/10/2012
Principal Author: Dixie Mills, MD, FACS