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
[{'content': 'Uicaria pigmentosa is a disorder of ? \nSelect and explain. \nA. Mast cells, B. Neutrophils, C. Eosinophils, D. Lymphocytes', 'role': 'user'}, {'content': "Answer: A \nExplanation: Mast cells REF: Rook's Er ed p. 22.31 Uicarial pigmentosa and mastocytosis are disorders of mast cells", 'role': 'assistant'}]