Q. A 37-year-old female presents to the emergency department with a 6-month history of episodic flushing, diarrhea, and wheezing. She also reports a recent diagnosis of right-sided valvular heart disease and a documented niacin deficiency. The patient has a family history of colon cancer and reports a 20-pound weight loss over the past year. Physical examination reveals elevated blood pressure and a palpable abdominal mass. Laboratory tests show elevated levels of urinary 5-HIAA. An abdominal CT scan reveals a 4 cm mass in the ileum and multiple liver lesions. A biopsy of the ileal mass shows prominent rosettes and positive staining for chromogranin A and synaptophysin. What is the most likely diagnosis based on this patient's symptoms and biopsy results?