This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Childhood tumors, Subject name: Pediatrics
A 2 year old child presents with scattered lesions in the skull. Biopsy revealed Langerhans giant cells. The most commonly associated is marker with this candition will be 
Select and explain. 
A. CD 1a, B. CD 57, C. CD 3, D. CD 68
A: CD 1a
Answer: A: CD 1a 
Explanation: In Langerhans cell histiocytosis,the hallmark feature is the presence of Birbeck granules on electron microscopy and positivity for S-100 protein and CD 1a. Reference:Essential pediatrics-Ghai,8th edition,page no:620.