MONDO_0020635 (anaplastic meningioma) is 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). Also known as: anaplastic (malignant) meningioma, malignant meningioma, meningioma, anaplastic, malignant.