[Malignant parasagittal meningioma appearing as a large subcutaneous mass]

We present a rare case of malignant meningioma appearing as an extracranial soft-tissue mass. A 34-year-old male was admitted with left parietal subcutaneous soft-tissue mass. Neurological examination on admission revealed right leg monoparesis and papilledema. Skull X rays showed hyperostosis of the left parietal bone. There was no evidence of bony destruction. CT and MRI showed a tumor with a large intracranial component, which was homogeneously enhanced. The tumor was totally removed by left ostoplastic craniotomy. The light-microscopic examination showed a meningothelial meningioma accompanied by malignant components with necrotic foci and mitotic figures. Tumor cells had invaded all the layers of the skull via the Haversian canals. We propose that hyperostosis with tumor invasion through all three layers of the skull should be considered as a malignant feature.