title: World Health Organization Grades II and III meningiomas are rare in the cranial base and spine.
abstract: OBJECTIVE
  This study was undertaken to assess a possible relationship between the tumor location and the incidence of World Health Organization (WHO) Grades II and III meningiomas.
  
  
  METHODS
  A retrospective review of 794 consecutive patients who underwent meningioma resection between January 1991 and March 2004 was conducted. Among these, 47 patients (5.9%) with WHO Grade II meningiomas and 16 patients (2%) with Grade III meningiomas were further analyzed. Tumor location was assessed using preoperative magnetic resonance imaging scans and/or operative reports. Histological grading was done according to the WHO 2000 Classification scheme.
  
  
  RESULTS
  WHO Grade II tumors were found in eight out of 289 (2.8%) cranial base meningiomas and in zero spinal meningiomas, compared with 39 out of 429 (9.1%) non-cranial base meningiomas. Grade III histology was encountered in two (0.7%) cranial base tumors and in one out of 76 (1.3%) spinal tumors, compared with 13 (3%) non-cranial base tumors. The combined incidence of Grades II and III meningiomas was significantly lower in the cranial base (3.5%) and spinal (1.3%) locations compared with non-cranial base locations (12.1%) (P < 0.001).
  
  
  CONCLUSIONS
  WHO Grades II and III meningiomas occur far less frequently in the cranial base and spinal locations. Tumors arising from these locations may have different mechanisms of tumorigenesis and/or progression compared with meningiomas arising from other (non-cranial base) regions.
authors.affiliation: Brain Tumor Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA.
authors.forename: Burak
authors.initials: B
authors.lastname: Sade
authors.forename: Ali
authors.initials: A
authors.lastname: Chahlavi
authors.forename: Ajit
authors.initials: A
authors.lastname: Krishnaney
authors.forename: Sean
authors.initials: S
authors.lastname: Nagel
authors.forename: Eugene
authors.initials: E
authors.lastname: Choi
authors.forename: Joung H
authors.initials: JH
authors.lastname: Lee
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D008579:Meningioma / Q000175:diagnosis*; D012189:Retrospective Studies; D019291:Skull Base / Q000473:pathology*; D019292:Skull Base Neoplasms / Q000175:diagnosis*; D013120:Spinal Cord Neoplasms / Q000175:diagnosis*; D013131:Spine / Q000473:pathology*; D014944:World Health Organization