Mammography and Dense Breast Tissue

Women with dense breast tissue should consider additional screening
By Caitlin Lopez, M.D.

In another step forward on the early detection of breast cancer, the Food and Drug Administration recently proposed new screening guidelines for women with dense breast tissue, which 50 percent of all women actually have. Massachusetts is among more than three dozen states which already require mammography screeners to tell women their breast density may make it harder to interpret their mammograms and that they should talk to their doctors about possible additional screening.

The first word of advice to a woman who’s told she has dense breast tissue is to take a breath and not be alarmed. Having dense breasts is very common and completely normal. Only a small percentage will ever have breast cancer. Knowing about breast density is simply one more piece of information that can help a woman understand her risk factors and stay healthy.

What is breast density?
Breasts are made up of glands, fatty tissue and fibrous connective tissue. The glandular tissue are the lobules and ducts that produce and transport milk.  The rest of the breast is a mix of fatty tissue and fibrous connective tissue which give breasts their shape and hold the glandular tissue in place. Dense breasts have relatively high amounts of glandular and fibrous connective tissue and relatively low amounts of fatty tissue. Your breasts are considered dense if more than 50 percent of your breasts are made up of fibrous connective and glandular tissue, versus fat.

Why is breast density an issue?
The main reason for the heightened scrutiny is the way dense breasts “read” on a routine mammogram. Because dense breast tissue appears bright white on a mammogram screen — just as cancer does — it can obscure malignancies. In other words, dense breasts potentially can mask or hide cancer. Women with dense breasts also appear statistically to have a somewhat higher risk of developing breast cancer. It’s not clear why and it’s not a hugely greater risk, but it’s another data point to keep in mind.

How is it breast density determined?
Breast density can only be determined by mammograms. It has nothing to do with breast size or firmness. A woman may think she has dense breast tissue because her beasts are firm, but how the breasts feels to the touch is not an indicator of density. Only when a radiologist looks at your mammogram can the density be determined. There are four categories of breast density, ranging from all-fatty tissue (which is the least dense), to tissue that is almost all glandular and fibrous, with very little fatty tissue (which is the most dense.)

What do I do if I’m told I have dense breast tissue?
If, when you receive your mammogram results in the mail, you’re told you have dense breast tissue, there’s nothing immediate you need to do – unless you’ve specifically been advised otherwise. But the next time you see your own doctor, be sure to talk to them about this information.  Discuss it in the context of your overall risk factors for breast cancer, including your own medical and family history.  That will help determine whether any other types of tests such as an MRI, a breast ultrasound or a 3D mammogram (breast tomosynthesis) would be advisable in your case. Again, those decisions would be made based on your overall risk factors, and not solely because it was determined you have dense breasts.

While breast density poses some challenges to routine mammography, annual mammogram screening for all women 40 and over remains the gold standard for detecting breast cancer and preventing deaths. Knowledge of breast density should be welcomed as another important piece of personal information that can help you manage your health risks and stay healthy.

Caitlin Lopez, M.D., is medical director of the Women’s Imaging Center at Berkshire Medical Center.