A 62-year-old woman presented with an uncommon case of anaplastic meningioma manifesting as recent memory disturbance. Magnetic resonance imaging revealed a mass located in the right temporal lobe. She became unconscious because of uncal herniation and underwent urgent surgery. The tumor was completely resected, except for a lesion tightly attached to arteries. Histological examination indicated the presence of anaplastic meningioma with an extremely high MIB-1 labeling index (70%). After 43 days, the patient developed local recurrence and dissemination in the left temporal lobe. The exceptionally high MIB-1 labeling index corresponded with a short tumor doubling time (8.2 days). Whole-brain irradiation and linear accelerator surgery for disseminated lesions were performed, and the tumor growth halted. Although meningiomas rarely show malignant behavior, corresponding to World Health Organization grade III, it is necessary to consider malignant behavior when treating meningiomas.
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