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': 'Which of the following is a marker for Langerhans cell histiocytosis? \nSelect and explain. \nA. CD 1a, B. CD 10, C. CD 30, D. CD 56', 'role': 'user'}, {'content': "Answer: A \nExplanation: The proliferating Langerhans cells in Langerhans cell histiocytosis are HLA-DR positive and express the CD1 antigen. Ref: Robin's Basic Pathology, 7th Edition, Page 441.", 'role': 'assistant'}]