Histology and ultrastructure of carotid body paragangliomas.Comparison with the normal gland

Abstract

Several surgically extirpated human carotid bodies and three paragangliomas of the carotid body region were compared by means of light and electron microscopy. Chief cells, both normal and neoplastic, are generously endowed with “dense-cored” cytoplasmic granules of the catecholamine type. The granules appear to develop in the Golgi region. In two of the tumors, an increased level of norepinephrine was detected by fluorimetric assay. Sustentacular (Schwannlike) cells are a constant parenchymal element in the normal glands and serve to convey unmyelinated nerve fibers into direct synapse with chief cells. All of the tumors lacked nerve endings, but sustentacular forms persisted as a prominent element in two cases. Evidence of neurosecretion in paragangliomas, despite lack of chromaffinity, indicates that the dichromate reaction is an inadequate substitute for biochemical and ultrastructural classification of neuroendocrine cells. The functional significance of secretion granules in normal chief cells remains to be elucidated.