This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
[{'content': "Lymphocytic infiltration is diagnostic in : \nSelect and explain. \nA. Brenner's tumour, B. Dysgerminoma, C. Dermoid cyst, D. Struma ovarii", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Dysgerminoma', 'role': 'assistant'}]