A 38-year-old female presents to the physician with complaints of excessive thirst and urination for the past 4 weeks. Her appetite has been normal and she has not had diarrhea. Blood chemistry showed mildly elevated glucose and glucagon. Physical examination reveals tenderness in the left upper quadrant and an erythematous necrotizing skin eruption on her legs. Radiographic studies show a tumor in the pancreas. Which of the following cells is responsible for this lesion?