Women’s breasts are made up of glandular tissue called lobules, which produce milk, and tiny tubes or ducts which carry the milk to the nipple. Breasts also have fibrous connective tissue and fatty tissue which give them their size and shape and hold the glandular tissue in place. Breasts with a lot of fibrous or glandular tissue, but not much fatty tissue, are considered dense. The reason for dense breasts is unknown, but usually, breasts become less dense with age.
Dense breasts are not abnormal but they do make mammogram images harder to read. Fatty tissue appears dark on a mammogram, whereas fibroglandular tissue appears as white areas. Because fibroglandular tissue and tumors have similar density, tumors can be harder to detect in women with denser breasts. The result is false-negative findings in which mammograms appear normal even though breast cancer is present. This occurs in about one-in-five screening mammograms and is found more typically in younger women who have denser breasts.
But according to Dr. Therese Bevers, medical director of MD Anderson’s Cancer Prevention Center, there should be no reason to worry: “Yes, it’s harder for mammograms to detect abnormalities in women with dense breasts. But, it’s not impossible. With digital mammograms, it’s easier to find anything unusual in your breasts.”i
Women with dense breast tissue between the ages of 25 and 39 should have a clinical breast exam every one to three years. At age 40, they should have a clinical breast exam annually along with a mammogram. Those with very dense breasts might need a breast MRI or ultrasound along with the mammogram.
Research has shown that dense breasts can be 6 times more likely to develop cancer. However, if you have dense breasts you can reduce your risks by lifestyle choices such as maintaining a healthy weight, exercising regularly, eating nutritious food, and avoiding alcohol and cigarettes. Most important, talk to your doctor about developing a special program for early detection that can give you peace of mind.
i Quoted in Adelina Espat, “Lumpy or Dense: Your ‘Breast’ Defense,” MD Anderson Cancer Center,” October 2012