A nonfunctioning paraganglioma of vagus nerve: an ultrastructural study.

The clinical, histological, and ultrastructural aspects of a cervical paraganglioma of the vagus nerve, in a 66-year-old white man, have been discussed in detail. Ultrastructurally, the tumor chief cells contained characteristic membrane-bound and dense-cored neurosecretory granules which ranged in size from 85 millimicron to 190 millimicron. Unlike earlier ultrastructural reports, the present study showed the presence of sustentacular or supporting cells. These cells were smaller, darker, polymorphic, and were commonly located at the periphery of a single or group of chief cells. Furthermore, unlike earlier reports on vagal paragangliomas, nonmyelinated nerve fibers and an occasional axon were identified in the present fine structure study.