Dense Breasts and Breast Cancer: A Connection?

Rumor has it that if you have dense breasts, then mammograms won't be effective. While there's some substance to that statement, it's not the whole story. Here, answers to your biggest questions about dense breasts.

How does breast density affect mammograms?

Breasts are made up of fatty tissue and connective tissue.  On mammograms, fatty tissue appears black and connective tissue appears white.  Women with dense breasts have more connective tissue than women with less-dense breasts.  That means a lot more "white" appears in their mammogram images. Cancerous tumors also appear white and that makes them harder to see with traditional mammography. 

Ever since mammography came into common use in the 1970s scientists have speculated about how breast density and breast cancer are connected.  That's because more women with dense breasts are found to have tumors within a year of a negative (normal) mammogram than women with less-dense breasts. 

Does this mean they grow more tumors or that the tumors were missed because they're hard to see?
A study published in the New England Journal of Medicine says women with dense breasts are at increased risk for breast cancer and develop it 4.7 times more frequently than women with less-dense breasts.

Leading breast cancer specialist and author, Dr. Susan Love, MD answers the question: Why would breast density increase breast cancer risk?

"Recent studies indicate that there are two aspects to developing breast cancer. First, you need the abnormal cell (seed). Second, the seed has to be in an environment (soil) that supports its growth and development. Many people now believe that dense breast tissue represents a "soil" or environment that is more supportive of breast cancer cells than less dense breast tissue. [The reason] why isn't yet known, but research that is now underway may soon provide us with some answers."

How do you know if you have dense breasts?
You can't tell just by looking, feeling, or by their size. Mammograms and other exams can help determine that.

If mammograms don't catch enough breast cancers in high-risk women, what should these women do?
Newer digital mammography, MRIs, and ultrasounds do a better job finding tumors than standard mammography. If you know you're at high risk because of your family and medical history, age, or because you use hormone therapy, ask your doctor when you should start receiving "screening" mammograms.  If your breasts are too dense to reveal enough information during screening procedures, your doctor will order further tests.

What else can you do to decrease your risks of developing breast cancer?
Breast cancer is a complicated disease with many contributing factors. Studies show that reducing risk factors like obesity, alcohol consumption, tobacco use, and (in some women), exposure to hormones like birth control pills and hormone replacement therapy, may reduce breast cancer development.  Increasing healthy behaviors like eating well, exercising regularly, reducing stress, and getting enough sleep may help, too.  See your doctor regularly for breast exams and to discuss the most appropriate screening techniques.



Dr. Susan Love Research Foundation
Breast Cancer