Malignant and atypical meningiomas: a reappraisal of clinical, histological, and computed tomographic features.

A series of 21 patients with atypical and malignant meningiomas is presented. Histological criteria such as high cellularity, typical and atypical mitosis, necrosis, infiltration of the underlying brain, poor differentiation, and distant metastasis define nonbenign meningiomas. Male predominance in this nonbenign group is significant when compared to a group of 205 benign meningiomas, which were also operated on. The malignant and atypical meningiomas are compared with the benign meningiomas, and special emphasis is placed on their computed tomographic features. The presence of tumor fringes (suggesting invasion of the brain substance) and intratumoral hypodense areas were both significant signs of malignancy of atypia. Radical surgical excision is still considered the treatment of choice.