How is glioblastoma multiforme (GBM) diagnosed?

Updated: Jul 01, 2019
  • Author: Jeffrey N Bruce, MD; Chief Editor: Herbert H Engelhard, III, MD, PhD, FACS, FAANS  more...
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No specific laboratory studies are helpful in diagnosing GBM. Tumor genetics are useful for predicting response to adjuvant therapy.

Imaging studies of the brain are essential for making the diagnosis, including the following:

  • Computed tomography

  • Magnetic resonance imaging, with and without contrast (study of choice)

  • Positron emission tomography

  • Magnetic resonance spectroscopy

  • Cerebral angiography is not necessary

Other diagnostic measures that may be considered include the following:

  • Electroencephalography: May show suggestive findings, but findings specific for GBM will not be observed

  • Lumbar puncture (generally contraindicated but occasionally necessary for ruling out lymphoma)

  • Cerebrospinal fluid studies do not significantly facilitate specific diagnosis of GBM

In most cases, complete staging is neither practical nor possible. These tumors do not have clearly defined margins; they tend to invade locally and spread along white matter pathways, creating the appearance of multiple GBMs or multicentric gliomas on imaging studies.

See Workup for more detail.

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