If you're a woman older than 40, you're probably familiar with mammography and ultrasound examinations for breast cancer screening. But a certain percentage of women — those at a high risk of breast cancer — may have an additional MRI screening.
"MRI shows the structure of masses, plus the enhancement pattern tells us about the vascularity — blood flow," said Linda Greer, MD, medical director for the HonorHealth Breast Health and Research Center. "Vascularity can help us decide if a biopsy is needed or not. More aggressive lesions tend to have more blood flow."
What happens during a breast MRI?
During an MRI breast exam, the technician injects a dye known as contrast so that blood flow shows up prominently. "With MRI, we sometimes can see cancers not yet visible on mammography or ultrasound," Dr. Greer said. Occasionally, tumors don't "enhance well on MRI and are better seen with ultrasound or mammography."
Which patients can breast MRIs help?
According to American Cancer Society guidelines, women at high risk of breast cancer who could benefit from breast MRI screenings include those who:
- Have an identified BRCA 1 or BRCA 2 gene mutation
- Have a first-degree relative with a BRCA 1 or BRCA 2 mutation and haven't had genetic testing themselves
- Had radiation therapy to the chest for another type of cancer between the ages of 10 and 30
- Have a genetic disease such as Li-Fraumeni syndrome, Cowden syndrome or Bannayan-Riley-Ruvalcaba syndrome, or have a first-degree relative with one of these syndromes
- Discover their lifetime risk is 20% or higher based on a risk assessment tool
When a patient is not considered high risk for breast cancer, MRI screenings are not currently recommended. Insurance won't cover MRI screening unless you're considered high-risk.
What happens after an MRI breast exam?
If a radiologist sees anything suspicious on MRI, the doctor would perform a biopsy, Dr. Greer said. A biopsy removes a small sample of tissue for further examination under a microscope.
"We biopsy using MRI as a visual guide if the lesion is only seen that way. If we think we can visualize the lesion with mammography or ultrasound during a biopsy, we will use one of those imaging approaches instead," Dr. Greer said.
What about false positives with MRI breast imaging?
When a patient is not considered at higher risk for breast cancer, MRI breast screenings are not recommended.
It's true that breast MRI has been found to be more sensitive in detecting cancers than mammograms. However, breast MRI screening can result in more false positives — the test finds something that initially looks suspicious but turns out not to be cancer.
MRI breast exams for average-risk women could result in unnecessary biopsies and added stress and anxiety.
For the right woman, however, MRI can be an effective diagnostic tool.