Clinical experience with incidentally discovered pheochromocytoma

Purpose: We reviewed 17 resected pheochromocytomas comprising 7 from symptomatic patients, and 10 unsuspected and incidentally discovered tumors. We compared various parameters concerning these 2 groups and investigated the features of the incidentally discovered pheochromocytoma. Materials and Methods: Patient gender and age, clinical symptoms and signs, tumor localization, detection methods, findings on imaging studies, urinary catecholamine concentrations, results of metoclopramide stimulation tests, treatments at operation and tumor size were evaluated. Furthermore, we compared the clinically diverse aspects arising between the symptomatic and incidentally discovered pheochromocytomas. Results: The 24-hour urinary noradrenaline and vanillylmandelic acid levels in the incidental cases tended to be lower than those in the symptomatic cases, while 24-hour urinary dopamine was significantly less (468 +/- 221 compared to 1,558 +/- 899 mu g/day, respectively). Typical symptoms of pheochromocytoma were noted in 6 patients (60%) in the incidental tumor group. The incidental cases had a markedly high false-negative rate (71%) as noted by the metoclopramide stimulation test, although the symptomatic cases had a 100% positive rate. On the other hand, the average diameter of incidental tumors was significantly larger than that of the symptomatic lesions (55.5 +/- 19.1 versus 35.9 +/- 12.1 mm., respectively). Conclusions: Clinical signs and findings in patients with incidental tumors were weaker than those with symptomatic disease although most incidental tumors functioned. Lower urinary catecholamine values in the incidental tumors were consistent with these results. However, the surgical risk for incidental tumors was the same as that for symptomatic lesions. Therefore, patients with incidentally discovered pheochromocytomas scheduled to undergo surgery should be treated accordingly.