Pathophys: tumors → secrete serotonin/histamine/kallikrein → broken down / excreted as 5hydroxyindoleacetic acid (5HIAA) in the urine
Usual location is gut: vasoactive substances usually metab in liver
Only get symptoms if liver mets, cirrhosis, or tumor outside gut

Signs / symptoms:
Flushing; Diarrhea
Wheezing / bronchospasm
Rightsided cardiac abnormalities (fibrous deposits on valves or myocardium)
Lung metabolism of serotonin prevents leftsided involvement
Wide swings in blood pressure
Cardiac arrhythmias

Diagnosis: urine 5HIAA

Treatment: surgical resection and/or octreotide