Malignant phaeochromocytoma with high circulating DOPA, and clonidine-suppressible noradrenaline.

Phaeochromocytoma, "perhaps the most fascinating of all tumors" [1], can present with a broad range of clinical manifestations [2]. Once suspected, the biochemical diagnosis is straightforward in most patients since plasma and urinary levels of noradrenaline and/or adrenaline, and urinary metabolites are well above those encountered in healthy subjects or patients with essential hypertension [3,4]. Exceptions to this general rule are well known, however, hence suppression tests have found favour, particularly in cases where catecholamine levels are within, or close to, the normal range [5-7]. We present a unique patient with malignant phaeochromocytoma whose plasma noradrenaline levels were in the high-normal range, and suppressed normally with clonidine administration. He had extremely high circulating levels of dihydroxyphenylalanine (dopa) which were not affected by clonidine, and different patterns of catecholamine concentrations in tumour tissue and plasma.