Diagnostic usefulness of sustentacular cells in paragangliomas: Immunocytochemical and ultrastructural investigation

Neuroendocrine tumors may derive either from neuroectoderm or endoderm. Bot h may present with a similar histologic pattern known as "Zellballen" regar dless of their histogenetic origin, making it difficult to separate the two different histogenetic entities in certain cases. To evaluate the usefulne ss of sustentacular cells in the recognition of tumors of paraganglionic or igin, the authors analyzed immunohistochemical and ultrastructural characte ristics of 25 paragangliomas and 19 pulmonary and 10 small intestinal carci noids. Sustentacular cells with characteristic dendritic features, strong i mmunoreactivity for S-100 protein, and agranular cytoplasm by electron micr oscopy were found consistently in the paragangliomas and not found in typic al carcinoid tumors, except for four examples of spindle cell carcinoid of the lung. The presence of sustentacular cells in tumors with "Zellballen" p attern therefore denotes paraganglionic origin.