Mediastinal meningioma.

A case of meningioma appearing to arise from the stellate ganglion and associated with a unilateral Horner syndrome of long standing is presented. Clinical absence of central nervous system involvement and a normal computerized tomographic scan of the brain favor the neoplasm as being a primary extracranial meningioma. Light and electron microscopy showed characteristic structural features. A brief review of the literature is made, and theories concerning the origin of extracranial primary meningioma are presented.