Carcinoid tumors of the gastrointestinal tract.

The gastrointestinal tract is the largest neuroendocrine system in the body. Carcinoid tumors are amine precursor uptake decarboxylase (APUD) omas that arise from enterochromaffin cells throughout the gut. These tumors secrete discrete bioactive substances producing characteristic immunohistochemical patterns. Most tumors are asymptomatic and detected at late stages. Hepatic metastases are commonly responsible for carcinoid syndrome. The small bowel is the most common location of carcinoids. Computed tomography scan and magnetic resonance imaging are useful in the detection of these tumors. The measurement of bioactive amines is the initial diagnostic test. Various treatment options, including somatostatin analogs, interferon, chemotherapy, surgery, hepatic artery chemoembolization, and surgery have emerged in the past two decades. However, the incidence and prevalence of carcinoid tumors has increased, while mean survival time has not changed significantly. The lack of standardized classification, federal support, and an incomplete understanding of the complications of this disease are some of the impediments to progress in treatment.