Diagnosis of pheochromocytoma.

The purpose of this article is to give an overview on recent advances in the diagnosis, localization by imaging and treatment of pheochromocytoma. Pheochromocytoma is a mostly benign tumor (malignancy rate 10-15%) which arises from chromaffin cells with excessive catecholamine production and secretion. Most tumors are localized in the adrenals but 15-18% of the lesions are found extraadrenally (paragangliomas). Pheochromocytoma is a rare form of secondary hypertension; it can also be found as a feature of familial disease (e.g. von Hippel-Lindau disease, MEN type II) due to genetic mutations of several genes that have been identified recently. In familial pheochromocytoma molecular genetic analysis has improved the diagnostic modalities. In such patients the tumor can occur bilaterally and patients often remain normotensive until the tumor produces sufficient catecholamines to have hemodynamic effects. The extreme importance of recognizing this tumor is evident from the fact that it can be successfully removed in about 90% of the cases, whereas if unrecognized the tumor poses great risk of death or devastating complications. Diagnostic screening includes measurement of catecholamines and their metabolites (metanephrines) in plasma and/or urine. Furthermore, pharmacological testing (e.g. clonidine suppression test) may be indicated in patients with moderately elevated catecholamines or when the diagnosis is still uncertain. Several imaging techniques are applied to localize the tumor. Abdominal CT scan is still considered the "gold standard" since about 98% of the tumors lie infradiaphragmatically. Magnetic resonance imaging (MRI) and MIBG-scanning are other useful methods. Recently, positron emission tomography (PET) based techniques have also been developed. After the diagnosis is made tumor removal following pharmacological pretreatment is the decisive therapeutic measure.