Meningothelial meningioma, light micrograph. Meningiomas are one of the commonest tumour types arising within the central nervous system and make up approximately 30% of primary intracranial tumours. 'Meningothelial' or 'syncytial' meningioma is one of the most common histologic subtypes of meningioma. It is a WHO grade I tumour. It is composed of meningothelial cells which are packed together in fascicles, whorls, and syncytia. The nuclei are bland and occasionally inconspicuous nucleoli can be noted. Mitotic figures are absent.