This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hypersensitivity, Subject name: Pathology
Toluidine blue staining is used for identification of? 
Select and explain. 
A. Mast cell, B. Fibroblast, C. Melanocyte, D. Macrophages
A: Mast cell
Answer: A: Mast cell 
Explanation: Mast cell Located in blood vessel and sub epithelial tissues Mast cells contain granules which contain proteoglycans. Granules stain positive with metachromatic stains such as:- Giemsa Toluidine blue