umls-concept:C0259785 | skos:definition | NCI: A rare, fast-growing tumor that forms in one of the inner layers of the meninges (thin layers of tissue that cover and protect the brain and spinal cord). Malignant meningioma often spreads to other areas of the body.,NCI: A malignant neoplasm of the meninges, exhibiting poor differentiation (anaplasia).,NCI: A WHO grade III meningioma characterized by the presence of malignant morphologic features, including malignant cytology and a very high mitotic index (20 or more mitoses per ten high power fields). | lld:umls |