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: Pathology
[{'content': 'Langerhan cells are not seen in: \nSelect and explain. \nA. Letterer siwe disease., B. Fabrys disease., C. Histiocytosis., D. None.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]