Neuroendocrine Tumors and Carcinoid Syndrome

A patient with a neuroendocrine tumor who develops episodic flushing and watery diarrhea may have carcinoid syndrome: tumor-derived mediators are acting beyond the tumor's local circulation. The immediate bedside pattern is flushing, secretory diarrhea, wheezing or bronchospasm, and—over time—signs of right-sided heart disease such as edema, hepatomegaly, ascites, or an elevated jugular venous pressure. The syndrome is more likely when a midgut tumor has hepatic metastases, because liver involvement allows serotonin to reach the systemic circulation, but bronchial and ovarian tumors can produce the syndrome without liver metastases. Diagnosis is not made from flushing alone. Pair the characteristic symptoms with biochemical confirmation using 5-hydroxyindoleacetic acid (5-HIAA). The practical safety distinction is whether symptoms are stable and recurrent or represent an acute carcinoid crisis, when hypotension, bronchospasm, and cardiovascular collapse can develop quickly.