Contributors: Roger E. McLendon and David S. Enterline
A paraganglioma may arise in paraganglia in different parts of the body (carotid body, glomus jugulare, glomus tympanicum, aortic bodies, orbit, and cauda equina). Synonyms for the tumor vary with tumor location and whether the neoplasm is chromaffin positive or negative: carotid body (chemodectoma), glomus jugulare (glomus jugulare tumor), aortic bodies innervated by the superior ganglion of the vagus nerve or nodose ganglia (vagal body tumors), glomus tympanicum (glomus tympanicum tumor), and orbital paraganglioma. Multiple endocrine neoplasia syndrome type IIA and multiple endocrine neoplasia syndrome type IIB are associated with  paragangliomas of the adrenal gland or sympathetic nervous system. Paragangliomas occur in the hereditary paraganglioma syndrome and heterozgous mutations have been found in three of the four genes [SDHB, SDHC, SDHD] that encode for mitochondrial succinate dehyrogenase  A familial tendency to carotid body paragangliomas has been described with an autosomal dominant inheritance pattern. The tumor is composed of round to cuboidal cells with round regular nuclei containing a granular "salt and pepper" chromatin pattern and zellballen. Cytologically the tumors reflect their tissue of origin with predominately chief cells associated with inconspicuous peripherally located sustentacular cells. The cytoplasm is variable in volume and is usually eosinophilic and finely granular, however it may be amphophilic or clear. Immunohistochemically, the cells react for anti-neuron specific enolase and chromogranin. The chief cells react with antibodies to synaptophysin and neurofilament proteins while the sustentacular cells react with antibodies to S100 and GFAP antibodies. Paragangliomas are generally benign tumors that may be cured with surgical resection. The success rate of surgery and/or radiotherapy varies from 85-95% based on symptomatic tumor regrowth. In cauda equina tumors, radiotherapy has little role in the initial treatment of the tumor. Paragangliomas of the cauda equina may cause back pain and symptoms of spinal cord compression while those arising in the glomus jugulare and temporal bone may invade the cranial vault and produce cranial nerve palsies. The glomus jugulare and glomus tympanicum tumors in particular may result in hearing loss and a sensation of fullness or pounding in the ear. The tumors only rarely produce symptoms attributable to catecholamine secretion. A functioning extra-adrenal paraganglioma is a component of  Carney triad.