Meningioma

: A type of brain tumor that starts within the meninges. These slow-growing tumors are sometimes associated with prior head trauma.

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A benign, encapsulated neoplasm of arachnoidal origin, occurring most frequently in adults; most frequent form consists of elongated, fusiform cells in whorls and pseudolobules with psammoma bodies frequently present; meningiomas tend to occur along the superior sagittal sinus, along the sphenoid ridge, or in the vicinity of the optic chiasm; in addition to meningothelial m., fibrous, transitional, metaplastic, psammomatous, secretory, clear cell, papillary, chordoid, and lymphoplasmocytic varieties are recognized. [mening- + G. -oma, tumor]

- cutaneous m. a lesion in the skin and subcutis composed of meningeal cells; occurs as a developmental lesion in children or as an extension of an intracranial m. in adults.

- malignant m. m. that either invades brain parenchyma or metastasizes.

- psammomatous m. a firm cellular neoplasm derived from fibrous tissue of the meninges, choroid plexus, and certain other structures associated with the brain, characterized by the formation of multiple, discrete, concentrically laminated, calcareous bodies (psammoma bodies); most of these neoplasms are histologically benign, but may lead to severe symptoms as a result of compressing the brain. SYN: sand tumor, Virchow psammoma.

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me·nin·gi·o·ma mə-.nin-jē-'ō-mə n, pl -mas also -ma·ta -'ō-mət-ə a slow-growing encapsulated tumor arising from the meninges and often causing damage by pressing upon the brain and adjacent parts

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n.

a tumour arising from the fibrous coverings of the brain and spinal cord (meninges). It is usually slow-growing and produces symptoms by pressure on the underlying nervous tissue. In the brain the tumour may cause focal epilepsy and gradually progressive neurological disability. In the spinal cord it may cause paraplegia and the Brown-Séquard syndrome. Some meningiomas may behave in a malignant fashion and can invade neighbouring tissues. Treatment of the majority of cases is by surgical removal if the tumour is accessible. The histological classification of malignancy is controversial, but some tumours may also require additional radiotherapy. Some patients have been known to have symptoms for as long as 30 years before the tumour has been discovered.

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me·nin·gi·o·ma (mə-nin″je-oґmə) [meninges + -oma] a benign, slow-growing tumor of the meninges, usually next to the dura mater, probably arising from cells associated with arachnoid villi. It may erode the skull or cause hyperostosis, and increased intracranial pressure is common. Meningiomas are now usually classified according to anatomic location; an older classification by histologic features exists, but histologic features have not been shown to influence clinical behavior.