Mayo Clinic Health Library

Question

Mammogram: Can it find cancer in dense breasts?

I've read that a mammogram is useless when it comes to detecting cancer in women with dense breasts. Is this true?

Updated: 12-06-2011

Answer

Dense breasts can make mammograms more difficult to interpret. But this doesn't mean a mammogram is useless for detecting cancer or other breast abnormalities in women with dense breasts.

Breast tissue is composed of fatty (nondense) tissue and connective (dense) tissue. The relative ratio of fatty tissue to connective tissue differs among women. As women age, their breasts tend to become less dense.

Dense breast tissue appears as a solid white area on a mammogram, and fat appears as a dark area. Mammogram X-rays do not penetrate — or "see through" — dense tissues as well as they do through fat. So, in women with dense breasts, mammograms are more difficult to interpret. Tumors also are dense tissue and appear as solid white areas on the mammogram. This can make it more difficult to detect a tumor in dense breasts because it looks a lot like the dense tissue that surrounds it.

Some studies have found that newer digital mammography does a better job detecting cancer in dense breasts than does mammography that uses film. A digital mammogram produces images on a computer screen that can be enhanced and magnified for closer viewing.

Many, but not all, medical centers offer digital mammography. Ask your doctor for a referral to a center that offers this technology if you feel it's best for you.