Gastroenteropancreatic Conceptually, there are two main types of<unk>  within the gastroenteropancreatic<unk> s (GEP-NET) category: those which arise from the gastrointestinal (GI) system and those that arise from the pancreas. In usage, the term "carcinoid" has often been applied to both, although sometimes it is restrictively applied to<unk> s of GI origin (as herein), or alternatively to those tumors which secrete functional hormones or polypeptides associated with clinical symptoms, as discussed. Carcinoid tumors Carcinoids most commonly affect the small bowel, particularly the ileum, and are the most common malignancy of the appendix. Many carcinoids are asymptomatic and are discovered only upon surgery for unrelated causes. These coincidental carcinoids are common; one study found that one person in ten has them. Many tumors do not cause symptoms even when they have metastasized. Other tumors even if very small can produce adverse effects by secreting hormones. Ten per cent (10%) or less of carcinoids, primarily some midgut carcinoids, secrete excessive levels of a range of hormones, most notably serotonin (5-HT) or substance P, causing a constellation of symptoms called carcinoid syndrome: * flushing * diarrhea * asthma or wheezing * congestive heart failure (CHF) * abdominal cramping * peripheral edema * heart palpitations A carcinoid crisis with profound flushing, bronchospasm, tachycardia, and widely and rapidly fluctuating blood pressure can occur if large amounts of hormone are acutely secreted, which is occasionally triggered by factors such as diet, alcohol, surgery chemotherapy, embolization therapy or radiofrequency ablation. Chronic exposure to high levels of serotonin causes thickening of the heart valves, particularly the tricuspid and the pulmonic valves, and over a long period can lead to congestive heart failure. However, valve replacement is rarely needed. The excessive outflow of serotonin can cause a depletion of tryptophan leading to niacin deficiency, and thus pellagra, which is associated with dermatitis, dementia, and diarrhea. Many other hormones can be secreted by some of these tumors, most commonly growth hormone that can cause acromegaly, or cortisol, that can cause Cushing's syndrome. Occasionally, haemorrhage or the effects of tumor bulk are the presenting symptoms. Bowel obstruction can occur, sometimes due to fibrosing effects of<unk>  secretory products with an intense desmoplastic reaction at the tumor site, or of the mesentery. Pancreatic<unk> s Pancreatic<unk> s (PanNETs) are often referred to as "islet cell tumors", or "pancreatic endocrine tumors" The PanNET denomination is in line with current WHO guidelines. Historically, PanNETs have also been referred to by a variety of terms, and are still often called "islet cell tumors" or "pancreatic endocrine tumors". originate within the pancreas. PanNETs are quite distinct from the usual form of pancreatic cancer, adenocarcinoma, which arises in the exocrine pancreas. About 95 percent of pancreatic tumors are adenocarcinoma; only 1 or 2% of clinically significant pancreas neoplasms are GEP-NETs. Well or intermediately differentiated PanNETs are sometimes called islet cell tumors;<unk>  cancer (NEC) (synonymous with islet cell carcinoma) is more aggressive. Up to 60% of PanNETs are nonsecretory or nonfunctional, which either don't secrete, or the quantity or type of products such as pancreatic polypeptide (PPoma), chromogranin A, and neurotensin do not cause a clinical syndrome, although blood levels may be elevated. Functional tumors are often classified by the hormone most strongly secreted by the pancreatic<unk> , as discussed in that main article. Other In addition to the two main categories of GEP-NET, there are rarer forms of<unk> s that arise anywhere in the body, including within the lung, thymus and parathyroid. Bronchial carcinoid can cause airway obstruction, pneumonia, pleurisy, difficulty with breathing, cough, and hemoptysis, or may be associated with weakness, nausea, weight loss, night sweats, neuralgia, and Cushing's syndrome. Some are asymptomatic.Animal<unk> s include<unk>  cancer of the liver in dogs, and devil facial tumor disease in Tasmanian devils. Familial syndromes Most pancreatic<unk> s are sporadic. However,<unk> s can be seen in several inherited familial syndromes, including: * multiple endocrine neoplasia type 1 (MEN1) * multiple endocrine neoplasia type 2 (MEN2) * von Hippel-Lindau (VHL) disease * neurofibromatosis type 1 * tuberous sclerosis * Carney complex Given these associations, recommendations in<unk>  include family history evaluation, evaluation for second tumors, and in selected circumstances testing for germline mutations such as for MEN1.
Neuroendocrine tumor
Pituitary adenoma
Metastatic insulinoma
Insulinoma
Glucagonoma
Granular cell tumor
Endocrine gland neoplasm
Glial tumor