This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hallmarks of Cancer, Subject name: Pathology
CD marker of histiocytosis is - 
Select and explain. 
A. CD1A, B. CD IB, C. CD1C, D. CD1D
A: CD1A
Answer: A: CD1A 
Explanation: Ans. is 'a' i.e., GDI A o CDIA is a T cell surface antigen important in dendritic cell presentation of glycolipids and lipopeptide antigeno It is used to diagnose Langerhans cell histiocytosis.o The presence of Birbeck granules in the cytoplasm of tumor cells is characteristic of Langerhans cell histiocyteo As Birbeck granules are not seen in all tumor cells by election microscopy the detection of S-100 and CDla expression by immunohistochemical techniques aids in the diagnosis.o Other immunohistochemical markers of Langerhans cell histiocytosis are: -HLA-DRLangerin (CD 207)CD 68