This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Pediatrics
CD marker of histiocytosisis: 
Select and explain. 
A. CD 1a, B. CD 1b, C. CD 1c, D. CD 1d
A: CD 1a
Answer: A: CD 1a 
Explanation: a. CD 1 a(Ref: Nelson's 20/e p 2484-2489, Ghai 8/e p 620-623)Immunohistochemistry shows: CD1a, S-100 or Langerin (CD 207) in Histiocytosis.