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
CD marker of histiocytosis is- 
Select and explain. 
A. CD IA, B. CD 1B, C. CD1C, D. CD1D
A: CD IA
Answer: A: CD IA 
Explanation: Tumour cells in histiocytosis typically express HLA -DR,S-100,and CD1a. Reference : Robbins and Cotran Pathologic basis of disease.South Asia Edition volume 1.page no. 622