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    Gastrointestinal Carcinoid Tumors Treatment (PDQ®): Treatment - Health Professional Information [NCI] - General Information About Gastrointestinal Carcinoid Tumors

    Epidemiology

    The age-adjusted incidence of carcinoid tumors worldwide is approximately 2 per 100,000 persons.[1,2] The average age at diagnosis is 61.4 years.[3] Carcinoid tumors represent about 0.5% of all newly diagnosed malignancies.[2,3]

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    General Information About Esophageal Cancer

    Incidence and Mortality Estimated new cases and deaths from esophageal cancer in the United States in 2014:[1] New cases: 18,170. Deaths: 15,450. The incidence of esophageal cancer has risen in recent decades, coinciding with a shift in histologic type and primary tumor location.[2,3] Adenocarcinoma of the esophagus is now more prevalent than squamous cell carcinoma in the United States and western Europe, with most tumors located in the distal esophagus. The cause for the rising...

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    Anatomy

    Carcinoid tumors are rare, slow-growing tumors that originate in cells of the diffuse neuroendocrine system. They occur most frequently in tissues derived from the embryonic gut. Foregut tumors, which account for up to 25% of cases, arise in the lung, thymus, stomach, or proximal duodenum. Midgut tumors, which account for up to 50% of cases, arise in the small intestine, appendix, or proximal colon, with the appendix being the most common site of origin. Hindgut tumors, which account for approximately 15% of cases, arise in the distal colon or rectum.[4] Other sites of origin include the gallbladder, kidney, liver, pancreas, ovary, and testis.[3,4,5]

    Gastrointestinal (GI) carcinoid tumors, especially tumors of the small intestine, are often associated with other cancers. Synchronous or metachronous cancers occur in approximately 29% of patients with small intestinal carcinoids.[3] However, it is possible that the association may be due in part to the serendipitous discovery of slow-growing carcinoid tumors, which are found while staging or investigating symptoms from other tumors.

    Histology

    The term carcinoid should be used for well-differentiated neuroendocrine tumors (NETs) or carcinomas of the GI tract only; the term should not be used to describe pancreatic NETs or islet cell tumors.[6] (Refer to the PDQ summary on Pancreatic Neuroendocrine Tumors (Islet Cell Tumors) for more information.) Data regarding carcinoids and other NETs, such as poorly differentiated neuroendocrine carcinomas, may be combined in some epidemiologic and clinical studies, rendering separate consideration difficult. Occurring nonrandomly throughout the GI tract are more than 14 cell types, which produce different hormones.[7] (Refer to the Cellular and Pathologic Classification of Gastrointestinal Carcinoid Tumors section of this summary for more information.) Although the cellular origin of NETs of the GI tract is uncertain, consistent expression of cytokeratins in NETs and the expression of the caudal-related homeodomain protein 2 (CdX2 protein), an intestinal transcription factor in endocrine tumors of the small intestine, suggests an origin from an epithelial precursor cell.[8]

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