Paraganglioma of the cauda equina: a histological, ultrastructural and immunocytochemical study of two cases with a review of the literature.

The clinical and pathological features of two paragangliomas arising in the cauda equina are described and compared with 14 previous reports. The light microscopic features were similar to those of paragangliomas from other sites, with a 'Zellballen' pattern of cells containing argyrophil granules. Electron microscopy showed densely staining membrane-bound granules, cilia and fibrous bodies in the cytoplasm. The last two features only occur in paragangliomas from this site. gamma-Enolase was demonstrated by the peroxidase-antiperoxidase technique for the first time in these neoplasms. This technique was also used to demonstrate cytokeratins, which appear to be associated with the presence of fibrous bodies. The pathological findings suggest that paragangliomas in this site arise from pre-existing paraganglia, possibly of the visceral autonomic group. The prognosis in cases treated by complete excision appears to be good.