CNS tumor
Meningeal tumors
Atypical meningioma

Topic Completed: 1 January 2014

Minor changes: 15 December 2020

Copyright: 2002-2021,, Inc.

PubMed Search: Atypical meningioma [title]

Jesse L. Kresak, M.D.
Anthony T. Yachnis, M.D.
Page views in 2020: 13,047
Page views in 2021 to date: 740
Cite this page: Kresak J, Yachnis A. Atypical meningioma. website. Accessed January 22nd, 2021.
Definition / general
  • WHO grade II
  • 5 - 15% of meningiomas
  • Diagnostic criteria either:
    • 4 - 19 mitotic figures/10 HPF OR
    • Brain invasion OR
    • Three of these histologic features:
      • Increased cellularity
      • Small cells with high N/C ratio
      • Large and prominent nucleoli
      • Patternless or sheet-like growth (loss of lobular architecture)
      • Foci of "spontaneous" or geographic necrosis
  • Note:
    • Invasion of dura, bone or soft tissue does not affect grading
    • Pleomorphic or atypical nuclei do not affect grade
    • Ki67 is not a true diagnostic criteria, however it is usually greater than 4% and up to 20%
  • May be associated with prior irradiation (J Neurosurg 2004;100:488)
  • 29% recur (vs. 9% of classic meningiomas and 50% of anaplastic meningiomas)
  • 10 year survival is 79% but 26% will assume a malignant phenotype
  • In one study, cyclin A and topoisomerase II staining predicted recurrence (Arch Pathol Lab Med 2002;126:1079)
Radiology images

Images hosted on other servers:

Atypical meningioma with surrounding edema

Primary lesion in left nasal cavity

T1 weighted MRI

Case reports
  • 36 and 70 year old women with optic nerve seeding of atypical meningiomas presenting with subacute visual loss (J Neurosurg 2013;119:494)
  • 44 year old man with atypical primary meningioma in the nasal septum with malignant transformation and distant metastasis (BMC Cancer 2012;12:275)
  • Elderly man with metastatic atypical meningioma (J Clin Neurosci 2000;7:69)
  • Gross total resection
  • Postsurgical radiation is often offered for atypical meningiomas, especially after a subtotal resection (J Neurooncol 2013;115:241)
  • Stereotactic radiosurgery
Gross description
  • Dural based
  • May be well circumscribed or focally adherent to brain parenchyma
  • Size can vary widely
Microscopic (histologic) description
  • May have identical histology to any grade I variant meningioma yet contain increased mitoses (4 - 19/10 HPFs)
  • May have increased cellularity or areas of small cell collections
  • May have sheet-like growth pattern
  • May have areas of spontaneous necrosis
  • May have macronucleoli
Cytology description
  • Squash prep shows similar histology as standard meningioma but may also show occasional mitoses or macronucleoli
Cytology images

Images hosted on other servers:

Meningothelial cells and whorl

Negative stains
Differential diagnosis
  • Hemangiopericytoma
  • Malignant meningioma with mitoses greater than 20/10 HPF
  • Meningioma with atypical features insufficient for criteria above
  • Necrosis due to prior therapy (which is not considered spontaneous)
Additional references
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