This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
Principal cell in granuloma is - 
Select and explain. 
A. Lymphocyte, B. Histiocyte, C. Langhans, D. Giant cell
B: Histiocyte
Answer: B: Histiocyte 
Explanation: histiocytes are also called epithelioid cells which are modified macrophages. They are elongated cells having a slipper-shaped nucleus. Macrophages and monocytes engulf the antigen and try to destroy it but since the antigen is poorly degradable these cells fail to digest and degrade the antigen and instead undergo morphologic changes to transform into epithelioid cells. ref robbins 9th ed page 98 .