Atypical and anaplastic meningiomas: prognostic implications of clinicopathological features.

OBJECTIVES To evaluate patient outcome and investigate the prognostic factors of high-grade meningiomas by adopting the 2000 World Health Organization (WHO) classification system. METHODS Between 1986 and 2004, 74 patients were diagnosed with high-grade meningioma: 33 with atypical and 41 with anaplastic meningioma. The mean follow-up was 58.5 months. We reclassified all surgical specimens, according to the 2000 WHO classification system, using two expert neuropathologists. RESULTS Forty of 74 meningiomas were reclassified as atypical meningioma and 24 as anaplastic meningioma. Overall and recurrence-free survivals were significantly longer in patients with atypical than in those with anaplastic meningioma: 142.5 versus 39.8 months and 138.5 versus 32.2 months, respectively (p<0.001). In patients with atypical meningiomas, brain invasion and adjuvant radiotherapy were not associated with survival; however, in the brain invasion subgroup, adjuvant radiotherapy improved patients' survival. In patients with anaplastic meningioma, the prognostic factors were brain invasion, adjuvant radiotherapy, malignant progression, p53 overexpression and extent of resection. The p53 overexpression was the only factor associated with malignant progression (p = 0.009). CONCLUSIONS The 2000 WHO classification has identified the truly aggressive meningiomas better than did the previous criteria. A precise meningioma grading system may help to avoid over-treatment of patients with an atypical meningioma as, once the tumour has "declared itself" by recurrence and histological features, it becomes a tumour that is poorly amenable to current therapies.