This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pathology
Which of the following is most reliable feature of malignat transformation of pheochromocytoma? 
Select and explain. 
A. Presence of mitotic figures, B. Capsular invasion, C. Vascular invasion, D. None
D: None
Answer: D: None 
Explanation: Determination of malignancy in pheochromocytoma is difficult. Benign pheochromocytomas show mitotic figures and vascular and capsular invasion. So none of the above said features will help to determine malignancy. Therefore,the definitive diagnosis of malignancy in pheochromocytoma is based exclusively on the presence of metastases. Ref: Robbins and cotrans 9e