Retroperitoneal malignant fibrous histiocytoma mimicking pheochromocytoma.

We report the case of a 52-yr-old man with a mass in the area of the left adrenal. The clinical features, MIBG uptake, and elevated urinary dopamine levels suggested the diagnosis of pheochromocytoma. He presented with unstable hypertension, tachycardia, weight loss, and the "inflammatory syndrome" (fever, leukocytosis, and high sedimentation rate). Clinical findings, preoperative radiographic (sonography, CT scan, [131I]MIBG scintigraphy), and endocrine evaluations (elevated 24-h urinary dopamine) were suggestive of a dopamine-secreting adrenal tumor. The mass was resected and on histologic examination showed the characteristic features of a malignant fibrous histiocytoma (MFH). The tumor cells were immunopositive for neuron-specific enolase (NSE), vimentin, CD-68, S-100, desmin, and immunonegative for chromogranin A, synaptophysin, neurofilament protein, and low-molecular-weight keratin, indicating that this tumor was not able to synthesize catecholamines. The prolonged retention of the tracer (MIBG) was interpreted as a consequence of obstructive hydronephrosis, while elevated urinary dopamine levels were assumed to be due to compression of the renal vessels by the large retroperitoneal mass. Copyright 2004 Humana Press Inc.