It’s easy to get alarmed when our mammogram report contains information we don’t understand. One term that appears on a lot of mammograms is the phrase “dense breasts”. What does this mean? Is it a good thing or a bad thing?
In order to understand what a “dense breast” is, it helps to know what breasts are made of. Like much of the rest of the body, breasts contain connective tissue, also known as fibrous tissue, that holds the body together. Like other organ systems, breasts also contain fatty tissue. Unlike any other organ, however, breasts contain mammary glands, whose function is to produce milk.
When a woman has dense breasts, her breasts contain more connective tissue and more glandular tissue. Not all dense breasts are equally dense. Some are dense throughout and some are dense only in certain areas.
How does dense breast tissue affect a mammogram reading?
When looking at a mammogram, fatty tissue appears dark, while connective tissue, glandular tissue and cancerous tissue appear white. When the breasts are dense, it is harder to spot white cancerous tissue, just as it is harder to see white clothing against a background of white snow. When breasts are not dense, cancer is easier to spot, just as it is easier to see white clothing against a dark background.
Because dense breast tissue can make it harder to spot cancerous tissue, mammogram reports now make note of the presence of dense breast tissue. These reports also classify the degree and type of breast density. The inclusion of breast density information in mammogram reports began relatively recently. It has now been mandated in some states. The newness of this change in mammogram reports is one of the reasons people may be unfamiliar with the concept of breast density.
Does dense breast tissue make it more likely that cancer will occur?
Extremely dense breast tissue increases the risk of breast cancer, although scientists are not sure why. Some women with very dense breast tissue may be referred for supplemental screening tests such as a breast MRI, a breast ultrasound or molecular breast imaging. The need for other screening tests will depend on the type and degree of breast density as well as the presence of other risk factors. Women whose breast tissue is classified as extremely dense should practice regular self-exams and seek care immediately if a lump is detected. Dense Breast Tissue & Cancer Risk: What You Should Know | Memorial Sloan Kettering Cancer Center (mskcc.org)
More research is needed to determine the best recommendations for supplemental screenings, as well as the nature of the relationship between dense breast tissue and the risk of breast cancer.