Correlation between histological grade and MIB-1 and p53 immunoreactivity in meningiomas

Objective: Meningiomas for the most part are slow-growing benign tumors, but complete removal can be difficult and recurrence is an issue. The aim of this study was to re-evaluate tumors diagnosed as meningioma previously in our hospital, according to the latest World Health Organization classification. We also examined the relationships among parameters such as brain invasion, histological grade and Ki-67 and p53 expression in these tumors. Materials and methods: Meningioma biopsy specimens numbering 60 (48 grade 1, 11 grade 11, and I grade III tumors) were examined immunohistochemically using monoclonal antibodies for Ki-67 (MIB-1) and p53 protein. The MIB-1 labeling index (LI) for each tumor was calculated as a percentage based on the number of stained cells per total cells counted. The level of p53 expression in each sample was semiquantatively evaluated as < 1 %, 1-10%, 10-70%, or > 70%. Any value > I % was accepted as presence of p53 expression. Results: Of the 60 meningiomas, 7 (11.7%) exhibited brain invasion. The mean MIB-1 LI values for the grade I and grade 11 tumors were 1.1% and 2.3%, respectively. The corresponding levels of p53 protein expression in these groups were 54.1% and 72.7%. The MIB-1 LI and the level of p53 expression in the one grade III meningioma were 6.7% and 10-70%, respectively. Histological grade was significantly correlated with MIB-1 LI and with p53 expression (p < 0.01 for both). Brain invasion was not correlated with histological grade, MIB-1 LI, or p53 expression. Conclusion: The results indicate that MIB-1 LI and p53 protein expression are good indicators of histological grade in meningioma and may be particularly valuable for distinguishing borderline atypical meningiomas. The number of cases was limited, but the findings also suggest that brain invasion is a prognostic parameter independent of grade, MIB-1 LI and p53 expression.