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What is a breast MRI?

Breast MRI (magnetic resonance imaging) is a type of imaging study that uses a large magnet, radio waves and a computer to produce detailed images of breast tissue. Unlike mammograms, a breast MRI doesn’t use X-rays (radiation).

Some of the most common reasons to perform a breast MRI include:

• To screen people who are at high risk for developing breast cancer because they have a strong family history, carry genes that increase their risk and/or have dense breast tissue. MRI is important because it may detect cancers that mammograms or ultrasounds can’t detect.
• To evaluate the extent of the cancer in people who have a new diagnosis of breast cancer.
• To evaluate for silicone breast implant ruptures.

Depending on the reason for a breast MRI, it may or may not require injection of contrast dye (called gadolinium). For many breast MRIs, a technologist or nurse will place an IV in your arm so they can inject contrast dye during the test. This helps a radiologist see normal and abnormal structures in your breast more clearly. This dye is different from the one used during CT scans.

What is the difference between a breast MRI and a mammogram?

Healthcare providers use mammograms and breast MRIs (and ultrasounds) to help detect breast cancer and other abnormalities.

However, mammograms are usually the first option for screening and diagnosis of breast cancer, particularly as mammograms are the only imaging test able to reliably identify microcalcifications — an early presenting sign of some breast cancers.

There are also differences in how the two imaging tests work.

Why would my healthcare provider order a breast MRI?

Your healthcare provider may recommend a breast MRI for several reasons, including:

• As part of breast cancer screening in addition to mammography if you’re at high risk for breast cancer (usually because of strong family history or genetic mutations, like BRCA1 or BRCA2).
• To gather more information after you’ve been diagnosed with breast cancer.
• To further evaluate breast abnormalities that are difficult to assess with mammography and breast ultrasound.
• To evaluate breast implants. MRI is the best imaging test to see if silicone breast implants have ruptured.

Breast MRI and breast cancer

Providers often recommend this test to provide more detail after diagnosing breast cancer. It can:

• Measure the extent of the cancer and see if it extends into your nipple, skin or underlying chest wall muscle.
• Look for other cancer or abnormal tissue in your breast.
• Check if you have any large lymph nodes in your armpit, which can be a sign that the cancer has spread (metastasized) to that area.
• Monitor the progress of breast cancer treatment, especially chemotherapy to shrink the tumor before surgery (neoadjuvant chemotherapy).

Breast MRIs may also be a helpful test to further evaluate lumpectomy sites in the years following breast cancer treatment. This is because scarring and recurrent breast cancer can look the same on mammography and ultrasound.

Does a breast MRI always show cancer?

An MRI can find some small breast tumors that a mammogram might miss, but it can also produce false-positive and false-negative results. For example, sometimes, a benign (noncancerous) piece of tissue in your breast can show up as a bright spot on the image, much like breast cancer. This would be a false-positive result. In any case, if a radiologist sees something in your breast tissue that doesn’t look normal, they may order additional tests such as a breast ultrasound or a biopsy to determine exactly what the finding is.

Alternatively, not all cancers will always show up on MRI that radiologists may be able to better see on other imaging tests, like a mammogram. This would be a false-negative result. This is one reason why the American Cancer Society and the U.S. Preventative Services Task Force don’t recommend breast MRI as a screening test by itself.

What type of results do you get from a breast MRI?

Depending on whether you got a breast MRI for screening purposes, diagnostic purposes or to evaluate known cancer, your MRI report may look different. In any case, your provider who ordered the breast MRI will discuss your results with you.

Radiologists all use the same standardized system to describe screening and diagnostic breast imaging (including mammogram, ultrasound and MRI) results. This system is called the Breast Imaging Reporting and Data System (BI-RADS). This system categorizes results on a scale of 0 through 6.

When should I know the results of my breast MRI?

The results of your MRI will be available in your electronic medical records account (if you have one) and should be available to the provider who ordered the test within one to two business days of your exam. Your provider will discuss the results with you.

A note from Cleveland Clinic

A breast MRI is a helpful tool for screening, diagnosing and evaluating breast cancer and other abnormalities. If you need a breast MRI and are worried about the procedure or have questions about it, don’t be afraid to ask your healthcare provider. They’re available to help and support you.