There are a few types of tumor that fall within a category somewhere between benign and malignant. Carcinoid tumors are the most often occurring of these rare types of midway growths. They have been called "cancers in slow motion" because even though they usually have the potential for ultimately being fatal, they mostly tend to grow slowly so that people afflicted with these tumors usually live for many years, sometimes even for a normal lifetime.
Carcinoid tumors are rare neuroendocrine lesions. Approximately 1,000 cases are seen each year in the United Kingdom. Most arise from the gastrointestinal tract. The commonest sites of the primary tumour are the appendix (30%), small bowel (20%), colon (20%) and stomach less than 10%. Tumors can also arise from the bronchial tree.
Carcinoid tumors arise from glandular endocrine-hormone producing cells that are widely distributed within the body but found in greatest amounts in the small intestine and then in decreasing amounts in the appendix, rectum, lung, pancreas and very rarely in the ovaries, testes, liver, bile ducts or other locations. The prognosis depends on where the original tumor is located, the likelihood of metastases becoming greater with increasing tumor size.
Carcinoid cells are capable of producing hormones. When carcinoid tumors have metastasised, those that produce large amounts of hormones and other potent chemical substances, and which often have spread to the liver, can cause "carcinoid syndrome" – hot red flushing of the face, diarrhea, and asthma-like wheezing attacks. Episodes of "carcinoid crisis" may be very infrequent and last only a few minutes at first but gradually occur more often as the disease progresses. Episodes are usually associated with abrupt low blood pressure and even fainting, although in a few cases the attacks are accompanied by high blood pressure. In many cases the symptoms of Carcinoid Syndrome, resulting from the hormones and chemicals produced, are worse than the symptoms from the growth of the tumor itself. Flushing may be precipitated by the ingestion of either chocolate or alcohol and is often associated with palpitations and episodes of hypotension. Clinical examination is often normal.
Not all functioning carcinoid tumors produce the same large variety of chemicals and hormones and it is not yet entirely clear which of the substances are responsible for each of the symptoms. Almost all of these tumors make serotonin and bradykinin.
Patients often present with vague right-sided abdominal pain which has often been present for a number of years, suggesting a right-sided abdominal mass or hepatomegaly. Many patients have had numerous normal investigations. Urgent surgery, has often been precipitated by the onset of intestinal obstruction.
Non-functioning carcinoid tumors are so slow-growing that many years may pass between the onset of any symptoms and the diagnosis. They can cause intermittent abdominal pain and then a change in bowel habits that may lead to intestinal obstruction. In some cases they cause obscure intestinal bleeding or sometimes don't declare themselves until they cause painful enlargement of the liver due to large deposits of carcinoid metastases that have spread to that organ. The diagnosis is not usually suspected prior to surgery but is then established by biopsy.
Carcinoid Syndrome, due to the presence of a functioning carcinoid tumor, is easily diagnosed when all of the features of the syndrome are present. However, the biggest impediment to making the diagnosis is not thinking of it because of its rarity: when it is considered, just one or two of the main symptoms may be enough to confirm suspicions.
Standard X-ray and imaging techniques can be helpful in finding a carcinoid tumor and identifying its spread. This could include routine chest X-ray, CT scans, MRI, barium enema or upper GI and small bowel X-ray studies. Sometimes upper and lower GI tract endoscopy is also helpful.
A now universally approved (though costly) way of finding carcinoid tumors, as well as other neuroendocrine tumors, is the OctreoScan. It is successful in 85% of carcinoids and consists of a (probably) harmless injection of a minute dose of a short duration radioactive isotope which is specifically attracted to, and concentrated in, carcinoid tumor tissue (and any other neuroendocrine tumor) where it lights up during a radiation scan of the entire body.
In most cases a firm diagnosis has not been established before an operative procedure has been performed.
There are many conventional treatments for carcinoid tumors and syndrome, although the choice of treatment and their applications can be quite complex. Carcinoid tumors vary greatly in their size, location, symptoms and growth, and therefore the treatment in each case should be individualized to what is best for each particular patient. The wide variety of treatments now available makes the outlook for most victims of the more aggressive carcinoids more hopeful than it used to be.
Surgery is often recommended and can be highly successful. In cases where somewhat larger tumors have spread to local tissues and local lymph nodes but are, along with these locally invaded tissues, still totally surgically removable, the average survival has been 8 years ranging up to 23 years.
Chemotherapy, with many choices available, has been in use since the early 1980s. Radiation is useful only for pain relief and regressing tumors when they have spread to the skeletal system and when they are causing severe pain.
Antihistamines and alpha adrenergic blocking drugs such as Dibenzyline are sometimes used to prevent Carcinoid Syndrome attacks. Certain very severe and prolonged carcinoid crises associated with bronchial (lung) carcinoids or some carcinoids of the stomach are responsive to treatment with corticosteroids (prednisone, Decadron) and Thorazine or Compazine.
Significant blood in the stool from a carcinoid tumor can cause bowel movements to become black.
The heart murmur seen in carcinoid syndrome is thought to occur secondary to high serotonin levels affecting the tricuspid valve and causing significant valvular insufficiency.
Weight loss can occur in carcinoid syndrome, as in most cancers, and the presence of diarrhea may contribute to further losses.
Patients with Carcinoid Syndrome sometimes have wheezing or asthma-like symptoms, making breathing difficult.
The facial flushing can be temporary or constant and usually appears suddenly on the face or neck. The flush looks deep red or purple. When this occurs, you may also feel warm, unpleasant, and have a rapid heartbeat. The flush may last only a few minutes in early stages of carcinoid syndrome and may last hours during later stages.
Diarrhea can occur along with facial flushing or by itself. Stools are watery and the diarrhea can be mild to severe. Episodes can occur several times each day and can interfere with daily life.
All carcinoid patients should avoid alcoholic beverages since these can precipitate carcinoid crisis attacks.
A high protein diet is often recommended. An adequate intake of the amino acid tryptophan, along with niacin, can prevent the tendency towards pellagra, which may otherwise occur from the excessive use of tryptophan by carcinoid tumors.
The measurement of CgA is considered "the gold standard" of chemical tests for confirming the diagnosis of carcinoid and neuroendocrine tumors and following their course.
Physical stress should be avoided since this can precipitate carcinoid crisis attacks.
Emotional stress can precipitate a carcinoid attack and should be avoided where possible.
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