Orbital nonchromaffin paraganglioma. A case report and review of the literature.

Nonchromaffin paraganglioma (NCP), also called glomus body tumor or chemodectoma, is rarely found in the orbit. The behavior of orbital nonchromaffin paraganglioma may potentially be more aggressive than in other head and neck locations. Diagnosis depends on electron microscopic demonstration of membrane-bound neurosecretory granules. Results of histopathologic study show a well-circumscribed lesion without a true capsule with alveolar or organoid arrangements of epithelioid cells within a reticulin framework with thin-walled blood vessels. Cells are polygonal with round or oval nuclei containing rare mitotic figures and pale-staining cytoplasm. Differential diagnosis includes alveolar soft-part sarcoma, alveolar rhabdomyosarcoma, neuroblastoma, carcinoid, and granular cell tumor. Of 29 previously reported cases of orbital NCP, 16 have been reclassified as alveolar soft-part sarcoma. The authors report a patient with an electron microscopically established orbital NCP, with the history of a contralateral glomus jugulare tumor irradiated 14 years previously.