Abstract

There is no definite histological criteria which can predict the biologic behavior of meningiomas, although resectability is the most important factor in terms of recurrence. For grading meningiomas, various factors have been studied, such as hypercellularity, nuclear pleomorphism, small cells with high N/C ratio, prominent nucleoli (PN), frequent mitosis, loss of architecture, focal necrosis (FN). We investigated 116 meningiomas to evaluate the correlation between the factors and the proliferative activity using AgNORs and MIB-1 labelling index (LI). They were divided into 3 groups: Group A includes meningiomas with none of the factors; group B with one of the factors; group C with two or more factors. MIB-1 LI was correlated with each factor, but AgNORs was not. There was a statistical difference among group A (<1.28%), B (2.7%) and C (5.1%) (p<0.05) using MIB-1 LI. FN was the most frequently associated with other factors, and it had the highest MIB-1 LI (6.31%). MIB-1 LI of group B was 5.1 2.3%. In group B, the most frequent combination was FN and PN, and it showed the highest MIB-1 LI (5.74%). This study indicates that FN and PN are important for diagnosis of atypical meningioma, and MIB-1 LI appears to be a useful method for estimating the proliferative activity of meningiomas, and 5% or more of MIB-1 LI could help in making a diagnosis of atypical meningioma.

• Keywords: Brain, atypical meningioma;Grading;Proliferative activity