WHO grade in meningiomas is useful for predicting recurrences. However, some of grade 1 meningioma can recur after total removal. I have examined the utility of several histological parameters for the prediction of a recurrence in benign meningiomas. Benign meningiomas rarely possessed some of histological features that were characteristic to high-grade tumors. That is, features of necrosis, brain invasion, prominent nucleoli, and small cell aggregation were rare, and those factors could not employed to distinguish recurrent and non-recurrent tumors in grade 1 meningiomas. In univariate analysis, cellularity, calcification, mitotic figures and MIB-1value (>2.0%) were signrificantly related to recurrence. In multivariate analysis, only MIB-1 value and calcification were significant. In recurrent benign meningiomas, MIB-1 value tended to decrease at the second surgery when MIB-1 value at the first operation was lower than 2.0%. The biological activity of meningiomas might be different between tumors with MIB-1 value less than 2.0% and those with higher MIB-1 value.
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