Characterization of morphologically benign biologically aggressive meningiomas

Meningiomas are presently categorized into three grades by World Health Organization (WHO). Grade I, in general, is expected to behave in a benign fashion. However, a borderline group of grade I meningioma also exists, which may behave aggressively.

To evaluate the proliferation index and p53 antigen expression of meningiomas and correlate with histological grade and clinical course.

All 123 cases of meningiomas, diagnosed between January 2000 and August 2007, were regraded according to WHO 2000 criteria. Immunostaining for Ki-67 antigen and p53 protein were performed on 68 cases selected for the study.

Six of the 68 cases presented with recurrence. Mean Ki-67 labeling index (Ki-67 LI) was 3.8%, 13.7%, 19.4% for grade I, II, and III cases, respectively. Multivariate analysis of mean Ki-67 LI showed statistically significant difference between subgroups. Mean p53 expression was found to be 15.5%, 57%, 60.8%, and 62.5% for grade I, II, III, and recurrent cases, respectively. Multivariate analysis of mean p53 expression showed no statistically significant difference between higher grades. All recurrent cases were histologically WHO grade I, and showed a high Ki-67 LI and p53 expression with mean Ki-67 LI and p53 expression of 8.6% and 62.5% respectively.

Utilization of markers for proliferation and cell cycle regulators in combination with histopathological features helps in the identification of a subset of biologically aggressive morphologically benign meningiomas.