Meningioma of the mandible.

This is the first case report to the authors' knowledge of a primary extracranial meningioma located in the mandible. Ultrastructurally, the tumor cells had intricate cellular membranes and desmosome-like attachment structures. Using immunohistochemical analysis, the tumor expressed both epithelial membrane antigen and vimen-tin. Although the origin of extracranial meningiomas has been attributed to proliferation of ectopic embryonal nests of arachnoidal cells, the proliferation of perineural cells of peripheral nerves also is possible as a result of the structural and functional similarities of perineural cell and arachnoid cells. The authors suggest that extracranial meningiomas may be more common than published reports indicate because of certain histologic similarities between these tumors, neurilemomas, and solitary neu-rofibromas.