Ki-67 proliferative index predicts clinical outcome in patients with atypical or anaplastic meningioma

Meningiomas represent the second most common central nervous system neoplasms in adults and account for 26% of all primary brain tumors. Although most are benign, between 5% and 15% of meningiomas are atypical (grade II) whereas 1-2% are anaplastic meningiomas (grade III). Although histological grade is the most relevant prognostic factor, there are some unusual cases in which establishing a diagnosis of high-grade meningioma following 2000 World Health Organization (WHO) histological criteria is extremely difficult. Therefore, the aim of the present study was to evaluate the predictive value of Ki-67 labeling index and its contribution to current WHO classification in predicting tumor recurrence and overall survival in patients with high-grade meningiomas. A total of 28 patients (with 16 atypical meningiomas and 12 anaplastic meningiomas) were evaluated for demographic, clinical, radiological and therapeutic variables, and for Ki-67 immunohistochemistry. Median Ki-67 labeling index in the whole series was 7.0 (0.5-31.5) with no differences with respect to the histological grade (P = 0.87). In the univariate analysis, Ki-67 labeling index and postoperative Karnofsky performance status were identified as significant prognostic factors of tumor recurrence and overall survival. The multivariate analysis demonstrated that Ki-67 labeling index is the only independent predictor of both tumor recurrence and overall survival. More importantly, this predictive value was maintained in both patients with atypical and patients with anaplastic meningioma.