This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Pathology
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 condition 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: The history is suggestive of langerhans cell histiocytosis( eosinophilic granuloma ).The tumour cells in addition to birbeck granules express HLA -DR, S- 100 and CD1a Reference : Robbins and Cotran Pathologic basis of disease.South Asia Edition volume 1.page no. 622