schwannoma

A benign, encapsulated neoplasm in which the fundamental component is structurally identical to a syncytium of Schwann cells; the neoplastic cells proliferate within the endoneurium, and the perineurium forms the capsule. The neoplasm may originate from a peripheral or sympathetic nerve, or from various cranial nerves, particularly the eighth nerve; when the nerve is small, it is usually found (if at all) in the capsule of the neoplasm; if the nerve is large, the neurilemoma may develop within the sheath of the nerve, the fibers of which may then spread over the surface of the capsule as the neoplasm enlarges. Microscopically, neurilemoma is composed of combinations of two patterns, Antoni types A and B, either of which may be predominant in various examples of neurilemomas. SEE ALSO: neurofibroma. SYN: neurilemoma, neuroschwannoma. [Theodor Schwann + -oma]

- acoustic s. SYN: vestibular s..

- vestibular s. a benign but life-threatening tumor arising from Schwann cells, usually of the vestibular division of the eighth cranial nerve; produces hearing loss, tinnitus, and vestibular disturbances, early and cerebellar, brainstem, and other cranial nerve signs and increased intracranial pressure in late stages. SYN: acoustic neurinoma, acoustic neuroma, acoustic s., acoustic tumor, cerebellopontine angle tumor, eighth nerve tumor.

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schwan·no·ma shwä-'nō-mə n, pl -mas also -ma·ta -mət-ə NEURILEMMOMA

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n.

see neurofibroma

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schwan·no·ma (shwah-noґmə) 1. a neoplasm originating from Schwann cells (of the myelin sheath) of neurons; the two types are neurilemomas and neurofibromas. Called also schwannoglioma and Schwann cell tumor. 2. neurilemoma.