This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Childhood Tumors, Subject name: Pediatrics
[{'content': 'Which of these is the most common cause of a posterior mediastinum mass in children? \nSelect and explain. \nA. Rhabdomyoma, B. Duplicated cyst of the esophagus, C. Thymoma, D. Neuroblastoma', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D. NeuroblastomaSeveral causes of posterior mediastinum mass in children are known; including neurogenic tumors (most common cause), foregut cyst, germ cell tumors, lymphangiomas and lymphomas. Since the most common neurogenic tumor in children is neuroblastoma, it should be the correct answer.', 'role': 'assistant'}]