Predictive factors for malignant pheochromocytoma: analysis of 136 patients

We evaluated the clinical characteristic, tumor feature and immunohistochemistry factors predicting malignant pheochromocytoma.

Between January 1999 and December 2008 we retrospectively reviewed the records of 136 patients with pheochromocytoma at Ruijin Hospital. We compared clinical characteristics (age, gender, symptoms and biochemical analysis), tumor features (site, weight and diameter) and the expression of 3 angiogenesis/metastasis related genes (VEGF, Cox-2 and MVD) by immunohistochemical analysis of benign vs malignant pheochromocytomas.

Of the 136 patients 105 (77%) had benign and 31 (23%) had malignant pheochromocytoma. Malignant tumors were larger and heavier than benign tumors, and accompanied by higher plasma metanephrine secretion (each p <0.001). Mean tumor catecholamine and preoperative 24-hour urinary metanephrine or normetanephrine were obviously higher in malignant than in benign tumors (p <0.001). Also, 25 malignant tumors (81%) were immunopositive for VEGF while only 24 benign tumors (23%) showed this characteristic (p <0.001). Microvessel density and the rate of positive staining for Cox-2 protein in malignant samples were higher than in benign samples (p <0.001).

Several promising predictive parameters are currently available to distinguish benign from malignant pheochromocytoma. Large (5 cm or greater) or heavy (250 gm or greater) tumors, multifocal and extra-adrenal tumors, early onset postoperative hypertension and higher plasma or urine metadrenaline are high risk factors predictive of malignant pheochromocytoma. Also, expression of the 3 angiogenesis or metastasis related genes VEGF, Cox-2 and MVD helps determine the diagnosis of malignancy and suggests strict followup.