What is the definition or description of: meningioma?

Meningioma: A meningioma is typically a slow growing tumor that is adjacent to the brain or extra-axial. The tumor arises from the arachnoid layer of the cerebral meninges. On imaging, it is a broad based tumor attached to the dura and tends to enhance with contrast dye. Meningiomas account for approximately 17% of intracranial neoplasms.

Meningioma : Meningiomas arise from the meninges, the membranous layers surrounding the central nervous system. These tumors are usually benign in nature; however, a small percentage are malignant. Many meningiomas are asymptomatic and require no treatment other than periodic observation. Symptomatic meningiomas are typically treated with either radiosurgery or conventional surgery.