Breast Cancer and MRI

Medically Reviewed by Jennifer Robinson, MD on August 11, 2022
3 min read

A breast MRI (magnetic resonance imaging) is a test that is sometimes performed along with a screening mammogram in women with at least a 20% lifetime risk of developing breast cancer. It is often done in women who have already been diagnosed with breast cancer to measure size and extent of the breast cancer. The American Cancer Society recommends yearly breast MRI and mammogram for high risk patients.

The breast MRI should  not be used in lieu of a breast biopsy to distinguish between benign (noncancerous) and malignant (cancerous) areas. Due to false positive results, this test may increase the number of breast biopsies that need to be performed. Although MRI may detect tumors in dense breast tissue, the presence of dense breast tissue is not a reason to have a breast MRI scan. Breast MRI scanning cannot detect tiny specks of calcium (known as microcalcifications), which account for half of the cancers detected by mammography.

Talk to your doctor about whether you should have an MRI of the breasts.

A breast MRI is safe. The test poses no risk to the average patient if appropriate safety guidelines are followed.

People who have had heart surgery and people with the following medical devices can be safely examined with MRI:

  • Surgical clips or sutures
  • Artificial joints
  • Staples
  • Most heart valve replacements
  • Disconnected medication pumps
  • Vena cava filters
  • Brain shunt tubes for hydrocephalus

Some conditions may make an MRI exam inadvisable. Tell your doctor if you have any of the following conditions:

  • Heart pacemaker
  • Cerebral aneurysm clip (metal clip on a blood vessel in the brain)
  • Implanted insulin pump (for treatment of diabetes), narcotics pump (for pain medication), or implanted nerve stimulators ("TENS") for back pain
  • Metal in the eye or eye socket
  • Cochlear (ear) implant for hearing impairment
  • Implanted spine stabilization rods
  • Severe lung disease
  • Uncontrolled gastroesophageal reflux (a condition causing severe heartburn)
  • A previous history of gadolinium allergy
  • Decreased kidney function
  • A tissue expander with magnetic port after mastectomy

In addition, tell your doctor if you:

  • Are pregnant
  • Weigh more than 300 pounds
  • Are not able to lie on your back for 30 to 60 minutes
  • Have claustrophobia (fear of closed or narrow spaces)

Allow 1 1/2 hours for your breast MRI exam. In most cases, the procedure takes 45 to 60 minutes, during which time several dozen images are obtained.

Before a breast MRI, personal items such as your watch, jewelry, and wallet -- including any credit cards with magnetic strips (they will be erased by the magnet) -- should be left at home or removed. Hearing aids should be removed before the test, because they can be damaged by the magnetic field. Secured lockers are typically available to store personal possessions.

You will be asked to wear a hospital gown during your breast MRI. You will also need to lie still throughout the procedure.

As the MRI scan begins, you will hear the equipment making a muffled thumping sound that will last for several minutes. Other than the sound, you should experience no unusual sensations during the scanning.

Certain MRI exams require that you receive an injection of a contrast material known as gadolinium. This helps identify certain anatomic structures on the scan images.

Feel free to ask questions or tell the technologist or your doctor if you have any concerns.

Generally, you can resume your usual activities and normal diet immediately after a breast MRI.

Your doctor will discuss the test results with you.