This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skin, Subject name: Medicine
[{'content': 'This patient had a 4-year history of diabetes. What is the diagnosis? \nSelect and explain. \nA. Bullous disease of diabetes, B. Necrobiosis lipoidica diabeticorum, C. Necrolytic migratory erythema, D. Pigmented purpuric dermatosis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Answer C. Necrolytic migratory erythemaGlucagonomas are rare neuroendocrine tumors that can cause diabetes and a rash known as necrolytic migratory erythema, which has a characteristic annular pattern of erythema with central crusting and bullae. The rash resolved after excision of a 7-cm glucagonoma from the tail of the pancreas.', 'role': 'assistant'}]