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Carcinoid (also carcinoid tumor) is a slow-growing type of neuroendocrine tumor originating in the cells of the neuroendocrine system. In some cases, metastasis may occur. Carcinoid tumors of the midgut (jejunum, ileum, appendix, and cecum) are associated with carcinoid syndrome. ==Signs and symptoms== While most carcinoids are asymptomatic through the natural lifetime and are discovered only upon surgery for unrelated reasons (so-called ''coincidental carcinoids''), all carcinoids are considered to have malignant potential. About 10% of carcinoids secrete excessive levels of a range of hormones, most notably serotonin (5-HT), causing: * Flushing * Diarrhea * Wheezing * Abdominal cramping * Peripheral edema The outflow of serotonin can cause a depletion of tryptophan leading to niacin deficiency. Niacin deficiency, aka pellagra, is associated with dermatitis, dementia, and diarrhea. This constellation of symptoms is called ''carcinoid syndrome'' or (if acute) ''carcinoid crisis''. Occasionally, haemorrhage or the effects of tumor bulk are the presenting symptoms. The most common originating sites of carcinoid is the small bowel, particularly the ileum; carcinoid tumors are the most common malignancy of the appendix. Carcinoid tumors may rarely arise from the ovary or thymus. They are most commonly found in the midgut at the level of the ileum or in the appendix. The next most common affected area is the respiratory tract, with 28% of all cases — per PAN-SEER data (1973 – 1999). The rectum is also a common site. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Carcinoid」の詳細全文を読む スポンサード リンク
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