Intraosseous intraneural perineurioma: report of a case with morphological, immunohistochemical and FISH study.

We report a case of an intramandibular intraneural perineurioma developed in the left dentary nerve. This tumour is rare and shows a typical histological, immunohistochemical and ultrastructural appearance: concentric whorls of perineurial cells EMA+ and PS100- around nerve fibers. This tumour must be distinguished from extraneural or soft tissue perineurioma, also composed of perineurial cells, with distinct clinical presentation and histological appearance, and from localized hypertrophic neuropathy, a reactive process frequently identified with intraneural perineurioma. Cytogenetic evidence for the neoplastic nature of this tumour is also presented in this report.