Oncocytic Pheochromocytoma with Cytokeratin Reactivity

Abstract

A large hemorrhagic pheochromocytoma (275 g) is described in a 38-year-old obese woman who had no history of sustained or sporadic hypertension. The tumor was unusual histologically because of the striking presence of oncocytic cells. Immunohistochemical studies revealed the positivity for neuron-specific enolase, synaptophysin, and cytokeratin CAM 5.2. Electron microscopy demonstrated neurosecretory dense core granules characteristic of a pheochromocytoma. Oncocytic pheochromocytoma was briefly documented in previous case reports but has not been well recognized. The expression of cytokeratin by pheochromocytoma is also very rare and has been described in a single study in the literature. This case had both unusual clinical and pathologic manifestations and is the first report of a pheochromocytoma with coexistence of oncocytic changes and cytokeratin immunoreactivity.