The potential risk factors for atypical and anaplastic meningiomas: clinical series of 1,239 cases.

BACKGROUND Determining factors that could accurately predict pathological features of meningiomas before histological diagnosis would help surgeons to proper balance the risk of operation and the resection grade. The aim of this study was to explore the potential risk factors for atypical (WHO Grade II) and anaplastic (WHO Grade III) meningiomas. METHODS Records of 1,239 patients between January 2009 and January 2013 were included in this research. Furthermore, immunohistochemistry with Ki67 was analysed in 368 samples. RESULTS The Pearson's chi-square test showed an increased risk for male gender for atypical and anaplastic meningiomas (P < 0.001) and an increased risk for cerebral convexity for atypical and anaplastic meningiomas (P < 0.001). However, significant differences in the terms of falx/sagittal sinus and intraventricular were not found. Patients with a Ki67 index ≥ 5% were significantly more likely to have atypical and anaplastic meningiomas than those patients with a Ki67 index < 5% (P < 0.001). In addition, the percentage of patients with a Ki67 index ≥ 5% in cerebral convexity meningiomas was higher than in non-cerebral convexity location (P = 0.006). CONCLUSIONS The results indicate that male gender, cerebral convexity are significant risk factors for atypical and anaplastic meningiomas.