During the 12-year period (1984-1996) 25 patients with pheochromocytomas were treated in our hospital. Among those tumors 23 were benign and 2 malignant with metastasis to liver, bones and lung. We examined all tumors clinically and histologically to evaluate their usefulness, in order to predict the prognosis of these tumors. The tumors were most common in the fourth and fifth decades. There was no sex predilection. The incidence of bilaterality was 4% and the tumors were more common on the right side. We examined histologically the growth pattern, the cellular atypia, the presence of necrosis, the capsular invasion, the vascular invasion, the presence of hyaline globules, nuclear pseudo-inclusions and periadrenal brown fat. The tumors were also examined immunohistologically for S-100 protein, NSE, chromogranin, synaptophycin and calcitonin. We found no definitive histological criteria to predict the biological behavior of pheochromocytomas. By immunohistochemistry no distinction was possible between the malignant and benign pheochromocytomas. The lack of S-100 protein immunoreacting satellite cells may indicate a malignant growth. In conclusion, the presence of metastasis remains the only absolute criterion for malignancy.

Key words: Adrenals, pheochromocytoma, immunohistochemistry.

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