Pathology of the Head and Neck

252 L. Michaels8Gross appearances are those of a granular or even grittymass. Microscopically, the neoplasm takes the sameforms as any of the well-described intracranial types ofmeningioma. The commonest variety seen in the middleear is the meningothelial type, in which the tumourcells form masses of epithelioid, regular cells often disposedinto whorls, which may be large or small. Fibroblasticand psammomatous varieties are also sometimesseen in the middle ear.Histological diagnosis of meningioma may be difficultbecause the above features are indistinct. Underthese circumstances immunocytochemistry may be ofsome diagnostic value. Meningiomas are negative formost markers, including cytokeratins. The majority ofmeningiomas, however, are positive for vimentin andepithelial membrane antigen.Nager’s review of temporal bone meningiomas indicatedthat only 2 out of 30 patients survived a 5-year period[78]. More recent experience of middle ear meningiomassignals a better outlook after careful local excision.In a recent study of 35 patients with follow up inwhich the tumour was sited mainly in the middle ear[116] surgical excision was used in all patients. Ten patientsdeveloped a recurrence from 5 months to 2 yearslater and 5 patients died with recurrent disease (mean,3.5 years); the remaining 30 patients were alive (n=25,mean: 19.0 years) or had died (n=5, mean: 9.5 years) ofunrelated causes without evidence of disease. Meningiomasof the middle ear behave as slow-growing neoplasmswith a good overall prognosis (raw 5-year survival,83%). Extent of surgical excision is probably the mostimportant factor in determining outlook because recurrencesdevelop in 28% of cases.8.3.2.7 RhabdomyosarcomaICD-O:8900/3Rhabdomyosarcoma is seen occasionally in the middleear of young children [126]. On rare occasions it isfound in the middle ear of adults [81]. The tympanicmembrane is usually eroded by the growth, which extendsinto the external canal. Grossly, the tumour islobulated and dark red with a haemorrhagic cut surface.Almost all temporal bone rhabdomyosarcomasare of the embryonal type, displaying mainly spindleor round primitive skeletal muscle cells, some of whichhave clear cytoplasm staining positively for glycogenand others have eosinophilic areas in the cytoplasm.Cross striations are unusual in this neoplasm. Immunohistochemicalmarkers for desmin, muscle-specificactin and antibodies against MyoD1 and myogeninconfirm this diagnosis.Rhabdomyosarcoma of the temporal bone is highlymalignant and spreads extensively into the cranial cavity,externally or to the pharyngeal region. Lymph nodeand bloodstream metastases frequently develop in thesepatients.8.3.2.8 Metastatic CarcinomaMetastasis of malignant neoplasms to the temporal boneincluding the middle ear is not uncommon. The breast isthe commonest primary source of metastatic tumours,followed by lung, kidney, stomach, larynx and cutaneousmalignant melanoma [43, 48]. Two distinct modesof spread may be involved in bringing the neoplasmsfrom their primary sites to the middle ear: (a) alongvascular channels in the petrous bone (these convey tumourdeposits to the temporal bone from distant sites),and (b) along nerves emanating from the internal auditorymeatus into the labyrinthine structures and bone.In this way, tumours reaching the meninges may spreadinto the temporal bone. In addition, direct spread maybring tumours into the ear from primary sites in areasadjacent to the temporal bone.8.4 Inner Ear8.4.1 Bony Labyrinth8.4.1.1 OtosclerosisOtosclerosis is a disease of the bony labyrinth, which,by involvement and fixation of the stapes footplate,leads to severe conductive hearing loss. Otosclerosishas some features of a hereditary disease, but its geneticsstill remain incompletely elucidated. Ultrastructuraland immunohistochemical evidence for measles virusand isolation and identification of DNA and RNA sequencesof that virus have been found in otosclerotictissue [18].Otosclerosis usually affects both ears symmetrically.The disease process is probably confined to the temporalbone. The pink swelling of otosclerosis may sometimeseven be detected clinically through a particularlytransparent tympanic membrane as a well-demarcatedand pink focus near the promontory. A characteristictranslucency of bone adjacent to the cochlea and anteriorto the footplate is identified on a CT scan.The lesion always commences in the otic capsuletissue anterior to the footplate of the stapes. In thisposition it does not produce symptoms. These occurwhen the otosclerosis invades the adjacent stapes footplateand produces fixation of that structure and thusconductive hearing loss. It later spreads widely in theotic capsule and may involve the round window ligament.Blood vessels are prominent and evenly dis-