The value of breast MRI for breast cancer detection remains uncertain. Some doctors believe MRI can distinguish a breast cancer from normal breast gland tissue better than other techniques. But breast MRI is expensive and requires highly specialized equipment and highly trained experts. Relatively few breast MRI centers exist, especially outside of major cities. And even at its best, MRI produces many uncertain findings. Some radiologists call these “unidentified bright objects,” or UBOs. MRI also cannot detect calcifications (calcium deposits in breast tissue that could be a sign of cancer). Finally, MRI can dislodge certain metal devices, such as pacemakers, in some people.
In some situations, however, breast MRI can be useful in gathering more information about an area in the breast that is suspicious or already confirmed to be cancerous. Possible uses include:
- evaluating a person who has a palpable mass (a mass that can be felt) that isn’t visible with ultrasound or mammography
- evaluating a lesion in the densely glandular breast of a young woman. Young women tend to have dense breast tissue, which makes it difficult to see abnormal areas on imaging studies.
- evaluating a person who has breast cancer cells in an underarm lymph node, but no breast mass that doctors are able to feel or to see on a mammogram. In these cases, where mastectomy is typically recommended, MRI can help find the precise site of the cancer’s origin within the breast. Finding the cancer’s site of origin can expand a woman’s treatment options from only mastectomy to include lumpectomy plus radiation.
- determining if a cancer is limited to one area of the breast, or if it is “multicentric” and involves more than one area. Knowing this affects treatment choices, since mastectomy is necessary for multicentric disease. MRI can be particularly useful for women with invasive lobular cancer, which has a tendency to be diffuse or multicentric.
- checking a woman’s other breast for signs of cancer after she receives her initial cancer diagnosis. The American Cancer Society recommends that breast MRI be used to check the other breast for any signs of cancer.
- examining breast tissue in women who have had silicone breast implants. MRI scanning can detect leakage from a silicone-filled breast implant, since it easily distinguishes silicone gel from surrounding normal breast and chest wall tissues.
After treatment for breast cancer, MRI can be useful for checking scar tissue in women who have undergone lumpectomy. Any significant changes could suggest a return of the breast cancer.
Finally, MRI scans of other parts of the body — such as the brain, spinal cord, or bones — may be useful in people who are known or suspected to have metastatic breast cancer (cancer that has traveled outside the breast to other areas of the body). For example, a person who has progressive back pain, or who develops new weakness or numbness in the arms or legs (not just hands or feet), can have an MRI scan of her back. The scan can help identify serious conditions such as the possible presence of a spinal tumor or brain metastasis.