Fig. (5) (A) and (B) The paraganglioma showing the characteristic "zellballen" architecture in hematoxylin & eosin staining (arrows). Note that the tumor cells were polyhedral with round or oval nuclei. (C) Intense immunoreactivity for chromogranin A in the tumor cells of paraganglioma (arrows). (D) Sustentacular cells immunostained for S-100 protein at the periphery of the tumor cell nests of paraganglioma (arrows). All figures are in 100X magnification.