[Clinical analysis of malignant meningiomas]

It seems generally accepted that meningiomas are benign tumors, and that malignant meningiomas are not common. The pathological criteria for judging whether meningiomas are malignant or not are controversial. Hemangiopericytic type, high cellularity, brain invasion, high mitotic rate, necrotic foci, and papillary type are regarded as histological characteristics of malignant meningiomas. Of a series of 105 patients with surgically treated meningioma, 25 patients demonstrated malignant characteristics (24%). The overall recurrence rate in our patients was 14%. The incidence of recurrence in 25 patients with pathologically malignant characteristics, and recurrence in 80 patients with pathologically benign characteristics were 32% and 9%, respectively. In comparison with benign meningiomas, recurrent factors in malignant ones included Simpson grade II operation, attachment of skull base, and no radiation-therapy. In conclusion, our criteria for malignant meningiomas have proved to be acceptable, and these cases should be treated with radiation therapy after surgery.