What Does It Mean if You Have Dense Breasts?

Did your last mammogram report say you have dense breasts? It’s more common than you think. Almost half of all women who get mammograms are found to have dense breasts. So, what does that mean?  

Understanding Dense Breast Tissue

Breast density describes the different kinds of tissue that show on your mammogram. Your breasts are made of fat, connective tissue, and milk ducts and lobules that together are called glandular tissue. Dense breasts have higher amounts of glandular and connective tissue and lower amounts of fatty tissue.Why does that matter? Because women with dense breasts have a higher risk for breast cancer than women with fatty breasts. Earlier studies suggest the risk can be four to six times higher, while more current research notes a 15 to 20% increase in risk. (These number differences come down to how studies are conducted, plus advances in technology that have improved breast cancer detection.)

How Do Doctors Determine Breast Density?

The radiologist who reviews your mammogram classifies your breasts according to these four groups:

• Almost entirely fat (about 10% of women)
• Some dense areas: scattered areas of dense glandular and connective tissue (about 40% of women)
• Many dense areas: numerous areas of glandular and connective tissue (about 40% of women)
• Extremely dense: almost all glandular and connective tissue and little fat (about 10% of women)

Dense breasts fall into groups C and D. Dense areas look white in a mammogram, the same color as cancer, making it tricky for health care providers to read the images and find breast cancer. The U.S. Food and Drug Administration now requires that mammogram reports include breast density, with the label “not dense” or “dense.”

Factors Affecting Breast Density 

Experts aren’t sure why having dense breasts increases your risk for cancer. Typically, breast density is inherited, but other factors can influence it. You may have higher breast density if you’ve used postmenopausal hormone replacement therapy or have lower body mass index. You are more likely to have lower breast density as you age, if you have had children, or if you have taken a breast cancer prevention drug called tamoxifen.

Should You Have Additional Tests? 

If you have dense breasts, speak with your provider about your personal risk factors for breast cancer and whether you should have more screening tests, such as 3-D mammography, a breast ultrasound, or a magnetic resonance imaging (MRI) exam. No screening recommendations beyond mammography have been established for dense breasts, although research is underway. And for women who are high risk for breast cancer, from factors including family history or inherited gene mutations, an MRI is recommended along with an annual mammogram.

Regular screening is important and can be lifesaving in catching breast cancer. You can also reduce your cancer risk by maintaining a healthy body weight, getting enough exercise, and limiting alcoholic drinks.