Introduction Tumor of neuroendocrine origin Location determines whether or not carcinoid syndrome is present no carcinoid syndrome if the GI mass has not metastasized to the liver liver metabolizes 5-HT arriving in the portal circulation carcinoid syndrome is observed if tumor exists outside GI system Most common site of carcinoid tumor is appendix but most common site of carcinoid tumor causing carcinoid syndrome is the small bowel Patients at risk for developing niacin deficiency all tryptophan is consumed in making excess 5-HT Presentation Symptoms diarrhea ↑ bowel motility flushing Phyical exam right-sided heart murmurs tricuspid insufficiency, pulmonary stenosis wheezing ↑ bronchospasm Evaluation Biopsy bright yellow tumor CT scan of liver detect masses Urinalysis 5-HT degraded to 5-HIAA and may be detected in the urine Treatment Surgery first line is excision Medical (if surgery not possible) octreotide somatostatin analogue controls flushing and diarrhea