Pathology of the Head and Neck

Ear and Temporal Bone Chapter 8 259Fig. 8.25. Low-grade adenocarcinoma of probable endolymphaticsac origin showing a papillary pattern. The epidermoid epitheliumon the right is probably that of the external auditory canal towhich the tumour had extended. Reproduced from Michaels andHellquist [68]Fig. 8.26. Low-grade adenocarcinoma of probable endolymphaticsac origin showing a thyroid-like glandular pattern from anotherarea of the tumour shown in Fig. 8.25. Reproduced from Michaelsand Hellquist [68]the seventh and eighth cranial nerves or their branches(Fig. 8.24) may pass through the lesion and their integritybe damaged by removal of the tumour it is recommendedthat diagnosis be made whenever the possibilityof this neoplasm is suspected at operation by examinationof frozen sections. If a diagnosis of lipomais made in this way the tumour should not be resected,since its further growth does not constitute a threat tovital structures [102].Low-grade adenocarcinoma of probable endolymphaticsac origin ( endolymphatic sac tumour): there is evidenceof the existence of an epithelial neoplasm of the endolymphaticsystem, mainly in the endolymphatic sac [35,38, 41]. Although of bland histological appearance andof slow growth the neoplasm seems to have considerableinvasive capacity and therefore the term “low-grade adenocarcinomaof probable endolymphatic sac origin” hasbeen applied. Other terms, such as endolymphatic sac tumourand Heffner’s tumour, are also in use. Some caseshave presented bilateral neoplasms of the same typeand some have also been associated with von Hippel-Lindaudisease [64]. The course of the tumour’s growth mayextend over many years. Tinnitus or vertigo, similar oridentical to the symptoms of Ménière’s disease, are presentin about one-third of patients. It is presumed that earlyobstruction of the endolymphatic sac leads to hydropsof the endolymphatic system of the labyrinth and so tothe Ménière’s symptoms. Imaging reveals a lytic temporalbone lesion, appearing to originate from the regionbetween the internal auditory canal and sigmoid sinus(which is the approximate position of the endolymphaticsac). There is usually prominent extension into the posteriorcranial cavity and invasion of the middle ear.In most cases the tumour has a papillary-glandularappearance, the papillary proliferation being linedby a single row of low cuboidal cells. The vascular natureof the papillae in some cases has given the tumoura histological resemblance to choroid plexus papilloma(Fig. 8.25). In some cases the tumour also shows areasof dilated glands containing secretion that has some resemblanceto colloid and under these circumstances thelesion may resemble papillary adenocarcinoma of thethyroid (Fig. 8.26). Such thyroid-like areas may evendominate the histological pattern. A few cases show aclear cell predominance resembling carcinoma of thekidney. On immunohistochemistry the epithelial cellsof this neoplasm contain antigens of cytokeratins. Sometumours contain glial fibrillary acidic protein. Thyroglobulinis always absent.It seems possible that many cases of the so-called“aggressive papillary middle ear tumours” may be lowgradeadenocarcinomas of the endolymphatic sac withextension of the neoplasm to the middle ear (see alsoSect. 8.3.2.3) [31]. Not all of such tumours may arise inthe endolymphatic sac [89].The histological appearances of low-grade adenocarcinomasof probable endolymphatic sac origin are indeedin keeping with the normal histological structureof the endolymphatic sac, which is lined by a papillarycolumnar epithelial layer.Cholesteatoma (epidermoid cyst) usually presentswith symptoms relating to its involvement of the seventhand eighth cranial nerves in the cerebellopontineangle. The histological appearance is similar to that ofmiddle ear cholesteatoma (see above). It is probably ofcongenital origin, but no cell rest has been discoveredfrom which it might arise.Cholesterol granuloma is a lesion of the petrous apexwith the typical features of cholesterol granuloma asseen in the middle ear and mastoid in chronic otitis media,and has been identified in recent years with increasingfrequency. At operation it appears cystic, the contentsbeing altered blood and cholesterol clefts with aforeign body giant cell reaction.