Atypical and Malignant Meningiomas
- Anaplastic, aggressive extra-axial tumors arising from malignant degeneration of typical meningiomas (TMs)
- WHO grade II (atypical meningioma [AM]) and grade III (malignant meningioma [MM])
- Most likely arise from dedifferentiation of TMs
- Increased mitoses, nucleus-to-cytoplasm ratio, necrosis, and nuclear atypia compared to TMs
- Sarcomatous degeneration, rapid growth, and invasion of brain parenchyma in MMs
- AMs account for <3% of all meningiomas
- MMs are uncommon
- Adults are most commonly afflicted (usually at a younger age than with TMs)
- Slight female gender predilection
- Treatment: surgical resection including adjacent bone; presurgical embolization; radiation
- Higher recurrence rates (MM > AM >> TM)
- Dura-based, extra-axial mass with necrosis, invasion of adjacent brain, and extensive peritumoral brain edema
- May arise at any location within the neuraxis
- AMs: cerebellopontine angle (CPA) cistern, tentorium most common
- MM: parasagittal or cerebral convexity
- Skull base and spine less commonly affected than with TMs
- Invasion and destruction of adjacent bone
- Ill-defined, hyperdense mass extending intracranially and extracranially
- Minimal calcification compared to TMs
- Extensive hypodense peritumoral edema
- Avid enhancement on contrast-enhanced CT imaging
- T1WI: variable signal intensity, often poorly defined tumor margins
- T2WI: variable signal intensity
- FLAIR: often marked hyperintense peritumoral edema
- DWI: reduced diffusivity (bright DWI, dark ADC)
- T1WI+C: avid enhancement with enhancing margins invading adjacent structures
- MR venography (MRV): evaluate patency and involvement of dural venous sinuses
- MRS: elevated alanine at short echo times (TEs) (1.3–1.5 ppm)
- MRI without and with intravenous contrast; MRV for dural sinus patency
For more information, please see the corresponding chapter in Radiopaedia.
Contributor: Rachel Seltman, MD
Cao X, Hao S, Wu Z, et al. Survival rates, prognostic factors and treatment of anaplastic meningiomas. J Clin Neurosci 2015;22:828–823. doi.org/10.1016/j.jocn.2014.11.022.
Moradi A, Semnani V, Djam H, et al. Pathodiagnostic parameters for meningioma grading. J Clin Neurosci 2008;15:1370–1375. doi.org/10.1016/j.jocn.2007.12.005.
Nagar VA, Ye JR, Ng WH, et al. Diffusion-weighted MR imaging: diagnosing atypical or malignant meningiomas and detecting tumor dedifferentiation. AJNR Am J Neuroradiol 2008;29:1147–1152. doi.org/10.3174/ajnr.A0996.
Osborn AG, Salzman KL, Jhaveri MD. Diagnostic Imaging (3rd ed). Elsevier, Philadelphia, PA; 2016.
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