Image Description
The tumor cells in pheochromocytomas contain abundant finely granular cytoplasm which can be deeply basophilic or amphophilic. The granularity is due to the presence of membrane-bound, electron-dense secretory granules containing catecholamines (as seen with electron microscopy). The nuclei are round or oval with one or more nucleoli. Some nuclei have "salt and pepper" chromatin characteristic of neuroendocrine tumors.