Definition: A benign, encapsulated neoplasm in which the fundamental component is structurally identical to the 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 cranial 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 schwannoma 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, schwannoma is composed of combinations of two patterns, Antoni types A and B, either of which may predominate in various examples of schwannomas.
Synonym(s): neurilemoma, neuroschwannoma
[Theodor Schwann + -oma]
See Also: neurofibroma
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