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: Medicine
Most common site of histiocytosis is - 
Select and explain. 
A. Bone, B. Skin, C. Lung, D. Liver
A: Bone
Answer: A: Bone 
Explanation: Langerhan's cell histiocytosis are malignant proliferation of dendritic cells or macrophages. These proliferating cells are actually Langerhan's cells of marrow origin.Reference :Harsh Mohan textbook of pathology 6th edition pg no 385.