An MRI is an effective test for detecting cancer in many parts of the body. It’s especially helpful at creating detailed images of soft tissue, including tumors. However, there are some types of cancer that it cannot detect.

Magnetic resonance imaging (MRI) is an imaging test that’s used to view the inside of the body. It uses magnets and radio waves to create cross-sectional images of your body from many angles. It helps doctors get a detailed look at soft tissues, which isn’t possible with some other types of imaging.

MRIs can be useful for finding a wide variety of cancers. They can detect tumors in many parts of the body and can help doctors pinpoint the size and location of the tumor. However, there are limitations with the types of cancer an MRI can detect.

This article takes a closer look at the effectiveness of MRIs at detecting cancer, when an MRI may not be helpful, and other tests that are often used to confirm a cancer diagnosis.

MRIs are a very effective way to find many types of cancer. They’re often better at finding tumors than other types of imaging tests such as X-rays or CT scans. The magnets and radio waves used during an MRI can create very detailed images.

Sometimes, contrast dye (a solution that’s injected into a vein) is used to make things more visible on MRI images. This helps provide more detail and clarity when it comes to tumors in areas such as the spinal cord.

MRIs can also be used to help stage cancer by helping doctors understand how far cancer has spread. Your doctor will use this information to determine the right course of treatment.

Once treatment begins, you may have additional MRIs to see how the tumor is responding to chemotherapy, radiation, and other treatments.

MRIs are very useful for detecting a range of cancers. Typically, MRIs are one part of the diagnostic process. They can help find and visualize tumors in cancers such as:

Sometimes, cancer may be detected when an MRI is ordered for some other reason. For instance, an MRI for joint pain could detect cancer in a nearby organ. This can sometimes mean diagnosing and treating cancer at an early stage before symptoms appear.

Can cancer be missed by an MRI?

MRIs can’t always detect cancer. It’s possible for an MRI to miss small tumors. Additionally, MRIs can sometimes produce unclear images that don’t show the tumor. This type of result is known as a false negative.

However, it’s unlikely that an MRI will be the only test you’ll have as part of a diagnosis for any type of cancer. If the results of your MRI don’t seem to line up with other test results, your doctor might order a second MRI or another type of imaging test.

If an MRI is unclear, you might have another MRI with contrast dye to help any tumors stand out. Or, you may have another test, such as an endoscopy, that allows doctors to get even closer to potential tumors.

MRIs aren’t the best choice in all situations. They’re a very effective tool for detecting tumors and damage to soft tissue. However, they don’t produce clear images of bones and bone matter. This means they typically can’t be used for bone injuries or bone cancer.

Additionally, you typically won’t have an MRI for blood cancers such as leukemia. These cancers are contained in blood and bone marrow and don’t cause tumors to form.

However, advanced blood cancers can cause organs, such as your spleen and liver, to swell. If your doctor suspects your organs have swollen, you might have an MRI to confirm this symptom.

An MRI is only one part of the cancer diagnostic process. It won’t be used alone to confirm a diagnosis. You’ll have a range of tests along with an MRI. The exact tests will depend on what type of cancer is suspected and what your doctor thinks is best.

Common diagnostic tests for cancer include:

  • Biopsies: A biopsy is done by removing a piece of tissue from the tumor and examining it under a microscope for cancer cells. There are several ways to perform a biopsy, such as with a long hollow needle, or as part of a surgical procedure. A biopsy is typically the only way to confirm a cancer diagnosis.
  • Imaging: In addition to an MRI, you might have additional imaging tests such as X-rays, CT scans, and PET scans to help doctors visualize tumors.
  • Endoscopy: Endoscopy is a procedure that’s done by inserting a thin tube with a camera and a light on the end into your body through an opening, such as your mouth, or through an incision. The tube is gently fed to the appropriate area, and the camera connects to a computer screen. This allows doctors to get an up-close look at organs, tissues, veins, and any tumor growth.
  • Blood tests: Blood tests look at levels of red blood cells, white blood cells, and platelets in your blood. This type of testing can be especially important for blood cancers, but many types of cancer can have an effect on your blood cells. Specific proteins and hormones in your blood may also be tested to help confirm a cancer diagnosis.
  • Urinalysis: A urinalysis measures the levels of substances like blood and proteins in your urine. It can help doctors measure how well your kidneys and liver are functioning, which can be affected by some types of cancer.
  • Genetic tests: Genetic testing is done to look for the genetic markers of cancer. In the case of some cancers, this may help doctors identify the type of cancer you have.

MRIs are useful imaging tests that can help detect cancer. Because an MRI is able to see soft tissue, it can create detailed images of tumor growth. They’re helpful for detecting many types of cancer.

However, MRIs can’t detect all cancers. They’re best at seeing tumor growth in organs and tissues. This means they’re not the best tool for detecting blood or bone cancers.

No matter what kind of cancer your doctor thinks you have, you’ll have multiple tests done to confirm your diagnosis. The process will typically include blood and urine testing, imaging tests, endoscopy, biopsy, and genetic testing. MRIs are often an important part of this process.