meningioma
A generally slow growing tumor attached to the dura mater. It is composed of neoplastic meningothelial (arachnoidal) cells. It typically occurs in adults, often women and it has a wide range of histopathological appearances. Of the various subtypes, meningothelial, fibrous and transitional meningiomas are the most common. Most meningiomas are WHO grade I tumors, and some are WHO grade II or III tumors. Most subtypes share a common clinical behavior, although some subtypes are more likely to recur and follow a more aggressive clinical course. (Adapted from WHO)