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
[{'content': 'Cell of origin of hairy cell leukemia is - \nSelect and explain. \nA. B-cell, B. T-cell, C. NK-cell, D. Dendritic reticulum cell', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Hairy cell leukaemia is an unusual & uncommon form of B cell malignancy characterized by presence of hairy cells in the blood & bone marrow & splenomegaly.Hairy cells are abnormal mononuclear cells with hairy cytoplasmic projections which are seen in blood,bone marrow & spleen.These cells exhibit CD19,CD20 & CD22 antigen.Reference: Harsh mohan textbook of pathology 6 th edition pg no 379', 'role': 'assistant'}]