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 spindly-looking cells with pink cytoplasm forming syncytial structures, whorls, and lobules separated by fibrovascular septa.