Temporal bone schwannoma.A schwannoma (acoustic neuroma or neurilemmoma) is a globular, firm, tan-yellow, solid to cystic neoplasm of nerve sheath (Schwann) cells. Schwannomas are the most common neoplasms of the ear and temporal bone. The vast majority arise at the cerebropontine angle, and 95% are unilateral and sporadic. Bilateral schwannomas and those that arise in young patients are highly associated with neurofibromatosis Neurofibromatosis Definition Neurofibromatosis (NF), or von Recklinghausen disease, is a genetic disease in which patients develop multiple soft tumors (neurofibromas). These tumors occur under the skin and throughout the nervous system. type 2 (NF2). Schwannomas affect men and women equally, usually in the fifth or sixth decade of life except in patients with NF2, who generally present at a younger age. Schwannomas are benign. The usual clinical manifestations are progressive, unilateral, sensorineural hearing loss Sensorineural hearing loss Hearing loss caused by damage to the nerves or parts of the inner ear governing the sense of hearing. Mentioned in: Tinnitus sensorineural hearing loss and tinnitus. These symptoms are occasionally accompanied by headache, vertigo, facial pain, and facial weakness. Imaging usually demonstrates that the internal auditory canal has been widened by a mass that is isodense to the cerebellum. These tumors arise from and are attached to the vestibular division of the VIIIth cranial nerve. Schwannomas are made up of cellular Antoni A areas with Verocay bodies (figure, A) and myxoid myxoid /myx·oid/ (mik´soid) mucoid. myx·oid adj. Containing or resembling mucus; mucoid. myxoid resembling mucus. myxoid adjective 1. , hypocellular Antoni B areas (figure, B). The cells are fusiform fusiform /fu·si·form/ (-form) shaped like a spindle; tapered at each end. fu·si·form adj. Tapering at each end; spindle-shaped. fusiform spindle-shaped. with elongated fibrillary cytoplasm, and their buckled to spindled nuclei exhibit little atypia. Nuclear palisading is common (figure, C). Small to medium-size vessels may exhibit perivascular perivascular /peri·vas·cu·lar/ (-vas´ku-lar) near or around a vessel. perivascular around a vessel. perivascular cellulitis hyalinization. Immunohistochemistry for S-100 protein will decorate the neoplastic cells, although usually unnecessary for diagnosis. Given the unique distribution of the tumor, the only common lesions considered in the differential diagnosis are meningioma meningioma /me·nin·gi·o·ma/ (me-nin?je-o´mah) a benign, slow-growing tumor of the meninges, usually next to the dura mater, which may invade the skull or cause hyperostosis, and often causes increased intracranial pressure; it is usually and neurofibroma neurofibroma /neu·ro·fi·bro·ma/ (-fi-bro´mah) a tumor of peripheral nerves due to abnormal proliferation of Schwann cells. neu·ro·fi·bro·ma n. . [FIGURES A-C OMITTED] The standard therapy is surgical removal via a number of different approaches (translabyrinthine, suboccipital, or middle cranial fossa) or by stereotactic stereotactic /ster·eo·tac·tic/ (-tak´tik) 1. characterized by precise positioning in space; said especially of discrete areas of the brain that control specific functions. 2. pertaining to stereotactic surgery. gamma knife surgery. The 5-year survival rate is greater than 90%. The risk of recurrence is very low. Suggested reading Mendenhall WM, Friedman WA, Amdur RJ, Antonelli PJ. Management of acoustic schwannoma. Am J Otolaryngol 2004:25:38-47. Michaels L, Beale T, Sandison A, Soucek S. Vestibular schwannoma. In: Barnes EL, Eveson JW, Reichart R Sidransky D, eds. Pathology and Genetics of Head and Neck Tumours. Kleihues R Sobin LH, series eds. World Health Organization Classification of Turnouts. Lyon. France: IARC Press: 2005:351-2. Lester D.R. Thompson, MD, FASCP From the Department of Pathology, Woodland Hills Medical Center, Southern California Permanente Medical Group, Woodland Hills, Calif. |
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