Carcinoid syndrome is a paraneoplastic syndrome associated with carcinoid tumors. It's primary symptoms are flushing and diarrhea, but it can lead to heart failure and bronchoconstriction. It occurs in about 5% of carcinoid patients.
Treatment usually focusses on the symptoms, using drugs that counteract the effect of the hormones involved. Carcinoid tumors are usually very hard to locate, often ruling out surgery. The side effects of the other available treatment, chemotherapy, is often worse than the syndrome's symptoms.