Pathology of the Head and Neck

Ear and Temporal Bone Chapter 8 251Fig. 8.15. Microsliced specimen of jugular paraganglioma removedat autopsy. Two slices of the temporal bone in the regionof the neoplasm are seen. The one on the left shows invasion ofthe temporal bone by the reddish paraganglioma from its apicalregion as far as the tympanic membrane. The slice on the right istaken at a higher level and shows sparing of the cochlea and bonylabyrinth by the tumourIn microscopic sections the tumour may be seen arisingfrom surface stratified squamous epithelium, itselfmetaplastic from the normal cubical epithelium.In certain areas an origin directly from basal layers ofcubical or columnar epithelium may be seen. There isno evidence that the epidermoid formation, a cell restthat occurs normally in the middle ear during development(see above), may be a source of squamous cell carcinoma.The neoplasm is squamous cell carcinoma withvariable degrees of differentiation. Atypical change andeven carcinoma in situ may be seen in some parts of themiddle ear epithelium adjacent to the growth. The modeof spread of the neoplasm from the middle ear epitheliumhas been ascertained in temporal bone autopsy sections[70] and this pattern has been confirmed by imagingin living patients. The carcinoma tends to growinto and erode the thin bony plate that separates the medialwall of the middle ear, at its junction with the Eustachiantube, from the carotid canal. This bony wall isnormally up to 1 mm in thickness and may be recognisedradiologically. Having reached the carotid canalthe growth will extend rapidly along the sympatheticnerves and the tumour is then impossible to eradicatesurgically. Another important method of spread isthrough the bony walls of the posterior mastoid air cellsto the dura of the posterior surface of the temporal bone.From there it spreads medially, enters the internal auditorymeatus and may then invade the cochlea and vestibule.Spread into the lamellar bone in both of these situationsis along vascular channels between bone trabeculae.A similar type of bone invasion may also occur fromother parts of the middle ear surface such as in the regionof the facial nerve. The special bone of the otic capsuleis, on the other hand, peculiarly resistant to directspread of growth from tumours within the middle ear,and even the round window membrane is not invaded.When invasion does occur it takes place after entry ofthe tumour into the internal auditory meatus and penetrationof the bone by way of the filaments of the vestibularand cochlear divisions of the eighth nerve. In thelater stages tumour grows extensively in the middle cranialfossa; it may also invade the condyle of the mandible.Death is usually due to direct intracranial extension.Lymph node metastasis is unusual and spread bythe bloodstream even more so [70].8.3.2.6 MeningiomaFig. 8.16. Jugular paraganglioma. The cells form small clusters,each surrounded by a row of flattened cells, probably sustentacularcells, and separated by blood vesselsICD-O:9530/0Meningioma is a benign tumour that usually growsintracerebrally, but is sometimes seen involving bonystructures around the brain including the middle ear.It arises from the pia-arachnoid cells of the meninges.These structures may be formed at a number of sites inthe temporal bone, including the internal auditory meatus,the jugular foramen, the geniculate ganglion regionand the roof of the Eustachian tube. Thus, meningiomasthat arise from them may be found in a wide area withinthe temporal bone itself [78].Meningioma of the middle ear affects females morethan males, shows an age range of between 10 and80 years (with a mean age of 49.6 years), with female patientspresenting at an older age (mean 52.0 years) thanmale patients (mean, 44.8 years) [116].The commonest temporal bone site for primary meningiomais in the middle ear cleft. In a recent study of36 cases, most of which involved the middle ear, but afew involved adjacent structures such as the external canalor temporal bone, only 2 showed a CNS connectionon radiography [116].Patients present clinically with hearing change, otitismedia, pain, and/or dizziness/vertigo.