Review Question - QID 210048

A 75-year-old man comes to his primary care physician because he has been having diarrhea and difficulty breathing. The diarrhea has been intermittent with frequent watery stools that occur along with abdominal cramps. Furthermore, the skin on his face and upper chest feels hot and changes color in episodes lasting from a few minutes to hours. Finally, the patient complains of loss of appetite and says that he has unexpectedly lost 20 pounds over the last two months. Based on clinical suspicion, magnetic resonance imaging is obtained showing a small mass in this patient's lungs. Which of the following is associated with the most likely cause of this patient's symptoms?