This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: FMGE 2019, Subject name: Pathology
[{'content': 'Most common anterior mediastinal tumour? \nSelect and explain. \nA. Thymoma, B. Neurofibroma, C. Pericardial cyst, D. Bronchogenic cyst', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The designation "thymoma" is restricted to tumors of thymic epithelial cells. Such tumors typically also contain benign immature T cells. The tumors usually occur in adults older than 40 years of age; thymomas are rare in children. Males and females are affected equally. Most arise in the anterior superior mediastinum, but sometimes they occur in the neck, thyroid, pulmonary hilus, or elsewhere.', 'role': 'assistant'}]