Objectives. The presence of metastatic lesions is the only acceptable fact to confirm malignant pheochromocytoma. Patients with malignant pheochromocytomas, however, have a very poor survival rate. The aim of our study was to postulate predictive values for malignant pheochromocytomas.

Methods. We evaluated symptoms, diagnostic modalities, treatment, and long-term follow-up of 86 patients with 85 benign and 10 malignant pheochromocytomas. Parameters from the benign were compared with those of the malignant pheochromocytomas.

Results. Preoperative 24-hour urinary dopamine was in the normal range for benign pheochromocytomas but increased in malignant pheochromocytomas (P <0.0001). Vanillylmandelic acid was elevated in both benign and malignant pheochromocytomas but higher in malignant than in benign tumors (P = 0.01). No differences could be shown in urinary epinephrine and norepinephrine samplings. Tumor location was divided into 77 adrenal (81%) and 18 extra-adrenal (19%) sites. Malignant pheochromocytomas were located more often at extra-adrenal sites (P = 0.03). There was no increased incidence of malignancy in patients with familial bilateral pheochromocytomas or multiple endocrine neoplasia. Tumors greater than 80 g in weight corresponded to malignancy (P <0.0001). Dopamine tumor concentration was higher in malignant than in benign pheochromocytomas (P = 0.01). Persistent arterial hypertension occurred in 9 (13%) of 72 benign and 6 (60%) of 10 malignant pheochromocytomas (P = 0.001). The 10-year survival rate was 94% for benign pheochromocytomas. All patients with malignant pheochromocytomas died within this period (P = 0.0001).

Conclusions. High preoperative 24-hour urinary dopamine levels, extra-adrenal tumor location, high tumor weight, elevated tumor dopamine concentration, and postoperative persistent arterial hypertension are all factors that increase the likelihood of malignant pheochromocytoma. Patients with these characteristics should have more frequent follow-up evaluations to identify malignancy at earlier states.