Breast cancer can go undetected in women who have dense breast tissue. They may need further specialized imaging exams to find or rule out the presence of a tumor.

A quick, 10-minute magnetic resonance imaging scan, or MRI, can detect more breast cancers than a digital 3D mammogram, reported a study published in the Journal of the American Medical Association.

In 2016, the ECOG-ACRIN Cancer Research Group set out to determine which screening test was better at identifying breast cancer in women with dense breasts. They compared the 3D mammogram, also known as digital breast tomosynthesis (DBT), with the brief MRI. (Other MRIs typically last at least 30 minutes.)

The results showed that in women with dense breasts, a brief MRI found almost 150% more breast cancers than DBT. Out of 1,444 women studied, the brief MRI detected cancer in 22 out of 23 women with breast cancer, while the 3D mammogram detected cancer in only 9 of 23 women.

Dense Breast Tissue

Some women have breasts that are dense, meaning the breasts have more supportive tissue, milk glands and milk ducts than they do fatty tissue. Fatty tissue appears dark and clear on a mammogram, but dense tissue shows up as white areas, which can hide tumors. Not only is breast cancer harder to detect in dense breast tissue, but women who have dense breasts are at a higher risk of developing breast cancer.

Other studies have seen similar results. A study completed in the Netherlands involving 1,355 women showed that MRI screening found cancer earlier than mammograms. Another study out of Canada found that MRIs were better than mammograms at finding breast cancer in women at high risk.

The American Cancer Society recommends that women between the ages of 45 and 54 get yearly mammograms. Women aged 55 and older should be screened every one to two years. Some women will need to have mammograms more often, and possibly additional tests, depending on their family history, genetics or other factors.

The take home

If you’ve been told by a doctor or radiologist that you have dense breasts, ask whether you need additional imaging tests, such as an MRI, to look for cancer that a regular screening mammogram might miss.