[The biological diagnosis of pheochromocytoma].

Pheochromocytomas are tumors secreting large amount of catecholamines. Elevation of blood pressure is the classical manifestation but frequently the tumors are silent and they have to be screened systematically. The biological diagnosis is essential to affirm the tumor before any imaging procedure. It needs to select the most sensitive and specific methods. The sensitivity of VMA, urinary catecholamines and plasma catecholamines assays is respectively 70%, 75%, 85%. Determination of methoxyamines in the urine or better in the plasma reaches a sensitivities of 98%. This represents the best tool for the diagnosis of pheochromocytomas. Only renal or heart failure decrease the specificity of the plasma methoxyamines assay.