[3] A large fraction of cases are diagnosed after routine surgery for bowel obstruction.
The tumor typically produces serotonin, Tachykinin peptides and other substances, which cause flushing, tachycardia, diarrhea and in some cases fibrosis of the heart valves.
[citation needed] There are often several small and highly fibrotic tumors present in the intestine.
Somatostatin analogues and Interferon decrease the secretion of hormones and the resulting symptoms.
[10] Traditionally, the primary tumor has been surgically removed even in the case of metastatic disease, although this was in 2017 shown not to improve survival in asymptomatic patients.