This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
Which of the following is the most reliable feature of malignant transformation of pheochromocytoma 
Select and explain. 
A. Presence of mitotic figures, B. Presence of metastasis to other organs, C. Vascular /capsular invasion, D. All the above
B: Presence of metastasis to other organs
Answer: B: Presence of metastasis to other organs 
Explanation: Ref Robbins 8/e p1159; 9/e p1135 There is no histological feature that reliably predicts clinical behaviour .Infact, cellular and nuclear pleomorphism, including the presence of giant cells, and mitotic figures are often seen in benign pheochromocytoma.while cellular monotony is paradoxical associated with an aggressive behaviour. Even capsular and vascular invasion may be encountered in benign lesions . therefore the definitive diagnosis of malignancy in pheochromocytoma is based exclusively on the presence of metastasis