Which of the following is most reliable feature of malignant transformation of pheochromocytoma?: (A) Presence of mitotic figures, (B) Presence of metastasis to other organs, (C) Vascular/ capsular invasion, (D) All of the above
Answer is B. - There is no histologic feature that reliably predicts malignant pheochromocytoma. - In fact, cellular & nuclear pleomorphism including presence of giant cells & mitotic figures are often seen in benign pheochromocytomas, while cellular monotony is paradoxically associated with aggressive tumors. - Even capsular and vascular invasion may be encountered in benign lesions. - Therefore, the definitive diagnosis of malignancy in pheochromocytomas is based exclusively on presence of metastases.