<prompt> Answer this question truthfullyWhat exactly is meningioma and what are the various classifications of this condition?  <response>: <reason> Meningioma has been classified into 3 groups by the WHO: benign classic meningioma WHO grade 1, atypical meningioma WHO grade 2, and anaplastic malignant meningioma WHO grade 3. The WHO grade 1 group grow very slowly and consists of about 9 variants. About 3 variants correspond to WHO grade II, their association with malignancy is not clear but they grow faster than benign meningiomas. About 2 variants correspond to WHO grade III. 