Objective: The clinical course of atypical and anaplastic meningiomas is heterogeneous. As malignant gliomas, aggressive meningiomas may arise de novo or transform from a benign tumor. This study aims to compare differences in clinical behavior, cytogenetics, cytokinetics, receptor status, and outcome between de novo malignant meningiomas and meningiomas that progressed to malignancy.
Methods: Data from 36 patients with atypical or anaplastic meningiomas were selected for retrospective analysis and divided into two subgroups: 1) de novo atypical or anaplastic tumors and 2) tumors that progressed from a lower grade. We analyzed data concerning patients' sex, age, tumor location, number of operations, status of hormone receptors, proliferative indices, cytogenetic findings, additional therapy, and survival. For meningiomas with progression, we calculated the interval between initial diagnosis and tumor progression.
Results: For atypical meningiomas, the subgroups had significant differences in status of progesterone receptors, proliferative indices, cytogenetics, and patients' outcome. The anaplastic group had similar differences, but they did not reach statistical significance because of the small numbers. There was a loss of part or monosomy of chromosome 10 and an increased monosomy or derivative chromosome 1 combined with monosomy of chromosome 14. These phenomena occurred mainly in patients with malignant transformation who had a worse outcome.
Conclusion: De novo malignant meningiomas and meningiomas with malignant transformation may represent distinct subgroups of atypical and anaplastic meningiomas.