Primary site of a<unk>  cancer of gut While most<unk> s are asymptomatic through the natural life and are discovered only upon surgery for unrelated reasons (so-called coincidental<unk> s), all<unk> s are considered to have malignant potential. About 10% of<unk> s secrete excessive levels of a range of hormones, most notably serotonin (5-HT), causing: * Flushing (serotonin itself does not cause flushing). Potential causes of flushing in<unk>  syndrome include bradykinins, prostaglandins, tachykinins, substance P, and/or histamine, diarrhea, and heart problems. Because of serotonin's growth-promoting effect on cardiac myocytes, a serotonin-secreting<unk>  tumour may cause a tricuspid valve disease syndrome, due to the proliferation of myocytes onto the valve. * Diarrhea * Wheezing * Abdominal cramping * Peripheral edema The outflow of serotonin can cause a depletion of tryptophan leading to niacin deficiency. Niacin deficiency, also known as pellagra, is associated with dermatitis, dementia, and diarrhea. This constellation of symptoms is called<unk>  syndrome or (if acute)<unk>  crisis. Occasionally, haemorrhage or the effects of tumor bulk are the presenting symptoms. The most common originating site of<unk>  is the small bowel, particularly the ileum;<unk>  tumors are the most common malignancy of the appendix.<unk>  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 commonly affected area is the respiratory tract, with 28% of all cases—per PAN-SEER data (1973–1999). The rectum is also a common site. Gastrointestinal<unk>  tumors are apudomas that arise from the enterochromaffin cells throughout the gut. Over two-thirds of<unk>  tumors are found in the gastrointestinal tract. Lung Histopathology of a typical<unk>  tumor of the lung, with prominent rosettes.<unk>  tumors are also found in the lungs. Other sites and metastases Metastasis of<unk>  can lead to<unk>  syndrome. This is due to the over-production of many substances, including serotonin, which are released into the systemic circulation, and which can lead to symptoms of cutaneous flushing, diarrhea, bronchoconstriction, and right-sided cardiac valve disease. It is estimated that less than 6% of<unk>  patients will develop<unk>  syndrome, and of these, 50% will have cardiac involvement. Goblet cell<unk>  This is considered to be a hybrid between an exocrine and endocrine tumor derived from crypt cells of the appendix. Histologically, it forms clusters of goblet cells containing mucin with a minor admixture of Paneth cells and endocrine cells. The growth pattern is distinctive: typically producing a concentric band of tumor nests interspersed among the muscle and stroma of the appendiceal wall extending up the shaft of the appendix. This makes the lesion difficult to suspect grossly and difficult to measure. Small tumor nests may be camouflaged amongst the muscle or in periappendiceal fat; cytokeratin preparations best demonstrate the tumor cells; mucin stains are also helpful in identifying them. They behave in a more aggressive manner than do classical appendiceal<unk> s. Spread is usually to regional lymph nodes, peritoneum, and particularly the ovary. They do not produce sufficient hormonal substances to cause<unk>  or other endocrine syndromes. In fact, they more closely resemble exocrine than endocrine tumors. The term 'crypt cell carcinoma' has been used for them, and though perhaps more accurate than considering them<unk> s, has not been a successful competitor.
Carcinoid
Analeptic
Psychogenic
Malignant 
Carcinogenesis
Carcinogen
Neuroskeptic
Toxicant