ABSTRACT
Neuroendocrine tumors (NETs) (old term: carcinoid tumors) are a diverse group of neoplasms with varying clinical behaviors. The tumors take their origin from the neuroendocrine cells that are widely distributed in the body. The most common sites of occurrence of NET are the gastrointestinal tract followed by lungs. Although most tumors are benign, some behave in an aggressive manner, especially the poorly differentiated types. A total of 10% of patients have functional tumors, i.e., they secrete hormones, especially in metastatic disease. NETs express somatostatin receptors, which have been targeted for diagnosis and therapy. A multidisciplinary approach is needed to treat these tumors. Surgery remains the mainstay of treatment and the only curative modality. Metastasis is not uncommon, especially to the liver, and requires intervention at most times, either surgically or alternative therapies such as ablation or radionuclide therapy. A small proportion of patients present with carcinoid syndrome and carcinoid crisis, the latter being life-threatening. In this chapter, we will discuss the etiology, molecular pathogenesis, clinical presentation, diagnosis and treatment of NET of the gut.
