A syndrome characterized by signs and symptoms caused by advanced carcinoid tumors. they include skin flushing, diarrhea, wheezing, and tachycardia.

Carcinoid syndrome is a paraneoplastic syndrome comprising the signs and symptoms that occur secondary to neuroendocrine tumors (formerly known as carcinoid tumors). The syndrome is caused by neuroendocrine tumors most often found in the gut releasing biologically active substances into the blood causing symptoms such as flushing and diarrhea, and less frequently, heart failure, vomiting and bronchoconstriction. .