This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Adrenal Gland, Subject name: Pathology
[{'content': 'Which of the following is most reliable feature of malignant transformation of pheochromocytoma? \nSelect and explain. \nA. Presence of mitotic figures, B. Presence of metastasis to other organs, C. Vascular/ capsular invasion, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: - 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.', 'role': 'assistant'}]