The paragangliomas appear grossly as sharply circumscribed polypoid masses and they have a firm to rubbery consistency.
 They are highly vascular tumors and may have a deep red color.

On microscopic inspection, the tumor cells are readily recognized.
Individual tumor cells are polygonal to oval and are arranged in distinctive cell balls, called Zellballen.
 These cell balls are separated by fibrovascular stroma and surrounded by sustentacular cells.

By light microscopy, the differential diagnosis includes related neuroendocrine tumors, such as carcinoid tumor, neuroendocrine carcinoma, and medullary carcinoma of the thyroid.

With immunohistochemistry, the chief cells located in the cell balls are positive for chromogranin, synaptophysin, neuron specific enolase, serotonin, neurofilament and Neural cell adhesion molecule; they are S-100 protein negative.
The sustentacular cells are S-100 positive and focally positive for glial fibrillary acidic protein.
By histochemistry, the paraganglioma cells are argyrophilic, periodic acid Schiff negative, mucicarmine negative, and argentaffin negative.
The paragangliomas appear grossly as sharply circumscribed polypoid masses and they have a firm to rubbery consistency.  They are highly vascular tumors and may have a deep red color.
On microscopic inspection, the tumor cells are readily recognized. Individual tumor cells are polygonal to oval and are arranged in distinctive cell balls, called Zellballen.  These cell balls are separated by fibrovascular stroma and surrounded by sustentacular cells.
By light microscopy, the differential diagnosis includes related neuroendocrine tumors, such as carcinoid tumor, neuroendocrine carcinoma, and medullary carcinoma of the thyroid.
With immunohistochemistry, the chief cells located in the cell balls are positive for chromogranin, synaptophysin, neuron specific enolase, serotonin, neurofilament and Neural cell adhesion molecule; they are S-100 protein negative. The sustentacular cells are S-100 positive and focally positive for glial fibrillary acidic protein. By histochemistry, the paraganglioma cells are argyrophilic, periodic acid Schiff negative, mucicarmine negative, and argentaffin negative.
Paraganglioma