This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Skin
Uicaria pigmentosa is a disorder of ? 
Select and explain. 
A. Mast cells, B. Neutrophils, C. Eosinophils, D. Lymphocytes
A: Mast cells
Answer: A: Mast cells 
Explanation: Mast cells REF: Rook's Er ed p. 22.31 Uicarial pigmentosa and mastocytosis are disorders of mast cells