This patient had a 4-year history of diabetes. What is the diagnosis?

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.