Naheed Moghal  ( Department of Pathology, Jinnah Postgraduate Medical Centre, Karachi. )
N. A Jafarey  ( Department of Pathology, Jinnah Postgraduate Medical Center, Karachi. )

A case of Chemodectoma of the middle ear is reported.

A 55 year old housewife presented to the ENT department of JPMC for noises in the left ear and impaired hearing for 5 years. For the last one year she also suffered from discharge and blee4ing from the same ear. Past history was non-con­tributory. Physical examination showed that the left external auditory canal was filled with a smooth mass having congested blood vessels on it. Mastoid x-ray films showed partial sclerosis of mastoid air cells. A clinical diagnosis of aural polyp was made and mastoidectomy with poly­pectomy done. Microscopic examination of H&E section showed a tumor composed of irregular clusters and nests of polyhedral cells separated by scanty connective tissue containing endothelial lined vascular spaces. The tumor cells contained scanty eosinophiic cytoplasm and large round to oval vesicular to densely staining central nuclei (Figure 1).

With special reticulin stain, groups of tumor cells were seen surrounded by reticulin fibres (Figure 2).

Chemodectoma (paraganglioma) is a rare tumor in general but it is the most common neoplasrn affecting the middle ear.¹ It arises from the non-chromaffin chemoreceptor tissue located in the middle ear. Other parts of the body where chemoreceptor cell nests are found are carotid body, jugular bulb, ganglion nodosum of vagus nerve, adventitia of ascending aorta, abdominal aorta and surface of lungs. All of these are of neural crest origin. They are responsive to changes in blood oxygen, carbondioxide and pH¹. The chemodectomas are all histologically similar and are classified by their location. In the ear, those arising from the tympanic plexus on the medial wall of middle ear are called glomus tym­panicum tumors while those arising in the adven­titia of jugular bulb are referred to as glomus jugulare tumors². Chemodectomas of the middle ear are benign, slow growing tumors that are locally invasive. Approximately 4% show a malignant change. They are more common in women and the peak incidence is about 50 years³. They are usually single but may be multicentric⁴. Multi-centric lesions show a familial distribution. The usual symptoms of chemodectomas of middle ear are diminished hearing, pulsating tinnitus, otalgia, otorrhoea, facial paralysis, other cranial nerve deficits, sensation of fullness or pressure in the involved ear. Biopsy is hazardous as they are highly vascular tumors but computerized are helpful in tomography and angiography making a diagnosis.^2,5

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2. Ghani, GA., Sung, Y. F. and Per Lee, .LH. Glomus jugulare tumors -. origin, pathology, and anaesthetic considerations. Anesth. Anaig., 1983; 62 :686.
3. Chen, K. T.K. and Dehner, L. P. Primary tumors of the external and middle ear. Arch. 11. A clinicopathologic study of 14 paragangliomas and three meningiomas. Otolaryngol., 1978; 104 :253.
4. Ervin, D.M. and Osguthorpe, J. D. X-ray study of the mouth. Multicentric paragangliomas. Ann. Otol. Rhinol. Laryngol., 1984; 93 : 96.
5. Chakeres, D. W. and LaMasters, D.L. Paragang­liomas of the temporal bone; high resolution CTstudies. Radiology, 1984; 150 :749.