- Unusual GI-based neuroendocrine tumors that produce hormones
- Flushing, diarrhea→ which can be profound, palpatations, puritus
- Sometimes wheezing
- Sometimes tricuspid and/or pulmonary valvular abnormalities
- Elevated 24h urine 5HIAA, serum Chromogranin A
- Imaging w/CT, MRI, PET; Somatostatin scintigraphy; Can also be visualized (and bx) endoscopically