Neuroendocrine cancer is also known as carcinoid cancer or carcinoid tumor. The carcinoid tumor is well known as the main contributor to carcinoid syndrome. Carcinoid syndrome is a collection of symptoms that is caused by the systemic release of the hormones from the neuroendocrine tumor/carcinoid tumor. Carcinoid syndrome is also known as Argentiffinoma syndrome or Flush syndrome.
Carcinoid tumor is a slow growing neuroendocrine tumor /neuroendocrine cancer . It is usually found in the appendix (40%), small bowel (20% with 15% commonly found in the ileum), and 15% in the rectum. Most of these tumors are found during the rectal biopsy and appendectomy. These tumors are benign and non secretory. However, some of the tumors are secretive and secrete peptide, prostaglandin, bradykinin, histamine and peptide hormones. These hormones are released into the portal circulation and later metabolized in the liver. The symptoms become more prominent when there is a hepatic metastases or the release of hormone into the systemic circulation from primary tumor which is originated outside of the gastrointestinal tract such as bronchus or extensive retroperitoneal structures.
Carcinoid syndrome is also associated with 10% of multiple endocrine neoplasia type 1 condition (MEN-1). Neuroendocrine tumor/carcinoid tumor is rare with an incidence of 1 in 1000 000. Carcinoid tumors are also found in autopsies (0.5%-0.75%). A Carcinoid / neuroendocrine tumor may also find in the bronchi (12%), colon , stomach, esophagus (10%) as well as the pancreas, biliary tract and ovary (3%).
The patient generally presents with bronchospasm, diarrhea and paroxysmal vasomotor disturbance. Paroxysmal/cutaneous flushing is common. It's present in 75%-90% of cases. The patient is initially presented with red purple flushing which begin in the face. The red purple flushes will later spread to the upper trunk and neck. The episodes of flushing may last for a few minutes. However in certain cases such as carcinoid tumor originating from the bronchus, the flushing may last for a few hours. The episodes of flushing may also be triggered by certain factors that include spicy food, alcohol and strenuous exercise or emotion. Besides facial flushing, patient may also present with facial telangiectasia.
Cramp abdominal pain that is confirmed by the audible peristalsis bruit may also present. The cramp abdominal pain is associated with an increase in the gut motility. These episodes of cramp abdominal pain will be followed later by diarrhea in 70% of cases. Severe dyspnea and wheeze which are the character of bronchospasm present in 25% of cases. Carcinoid syndrome may also present with a right sided heart murmur. The right sided heart murmur may include tricuspid stenosis, tricuspid regurgitation and pulmonary stenosis. Carcinoid crisis is also well known as one of the complication of the carcinoid syndrome and the patient is presented with severe hypotension and tachycardia.
Gross pathology of neuroendocrine tumor/carcinoid tumor may reveal that this tumor is a solid and yellow tan in appearance. It is classified as hindgut, mid gut and fore gut tumor depending on the sites of origin . The primary tumor is usually surrounded by an area of fibrosis. Microscopically, the tumor originates from the APUD cell which is also known as enterochromaffin cells. Carcinoid tumor is presented as dense cytoplasmic granule when it is viewed under electron microscopy . These granules usually contain peptide hormones.
The differential diagnosis of carcinoid syndrome due to neuroendocrine/carcinoid tumor may include idiopathic flushing. Idiopathic flushing is different from carcinoid syndrome in terms of duration of the symptoms. Idiopathic flushing is presented with longer duration of hypotension, syncope and palpitation. Idiopathic flushing is more common in young female compared to carcinoid syndrome.
The laboratory test to diagnose carcinoid syndrome may include 24 hour urine collection. 24 hour urine collection is useful to measure the 5 HIAA or 5 hydroxyindoleacetic acid which is a metabolite of 5 hydroxytryptamine /serotonin. The false positive result is associated with certain medication such as caffeine, acetaminophen, reserpine and guaifenosin. Banana, avocado, walnut, pineapple and eggplants may also related to a false positive result. Therefore before performing this test, the patient is advised to stop from taking these medications and have a restricted diet. The blood test is useful to measure the level of fasting gut syndrome and plasma concentration of Chromogranin B.
The imaging technique may include chest x ray, CT scan /MRI scan , and radioisotopes scan. Chest x ray is useful to detect the present of carcinoid tumor/neuroendocrine tumor in the bronchus. CT scan or MRI scan is useful to localize the tumor. Besides that CT scan oof the liver or CT scan of the abdomen or radionuclide scan of the spleen is useful in detecting any liver metastases. Radioisotopes scan such as iodine -123 radiolabeled (123-ISS) somatostatin analogue is useful in localizing and detecting any endocrinological carcinoid tumor with somatostatin receptor. Any previously undetected or any metastatic lesion can be detected by scanning with radiolabeled octreotide.
The treatment of carcinoid/neuroendocrine tumor may include advice/non pharmacological treatment. In this category, the patient is advised not to take spicy food, alcohol and performing the strenuous exercise. The patient is advised to avoid ethanol that may precipitate facial flushing.
Surgical treatment may involve the resection of the tumor or debulking of the tumor. It can be palliative in case where the tumor has metastases . In this case, the patient may present with long period of asymptomatic. Any localized tumor however may be cured with surgical resection. Severe vasomotor abnormalities (severe hypotension and tachycardia) and bronchospasm may happen due to surgical manipulation of the tumor. The condition is known as carcinoid crisis. Carcinoid crisis is treated with infusion of octreotide, IV hydrocortisone and IV antihistamine.
Any cases of hepatic metastases are treated with percutaneous embolization of the hepatic artery. This procedure able to decrease the bulk of tumor in the liver which will provide a palliative treatment in some cases of hepatic metastases.
Chemotherapy treatment is considered in any cases where the tumor is not resectable or recurrent of carcinoid tumor . Cytotoxic chemotherapy may include a combination of chemotherapy such as streptozotocin and 5 fluorouracil. Interferon alpha is also useful in cases of hepatic metastases. The rate of success in using chemotherapy is still limited.
Supportive treatment may include loperamide, codeine or Lomotil in case of diarrhea , aminophylline or albuterol in case of bronchospasm, somatostatin analogue for flushing and diarrhea that occur at the same time and the combination of H1 and H2 receptor antagonist such as diphenhydramine and ranitidine for flushing only symptom. Other treatment may include rehydration for diarrhea and ondansetron and cyproheptadine to alleviate the symptoms. Nutritional deficiency may occur because the tumor required tryptophan to synthesize serotonin and this may result in pellagra. Therefore nutritional support such as niacin supplement therapy is useful.
In chronic cases of neuroendocrine tumor, multidisciplinary approach is required. The treatment may require the decision made by the gastroenterologist, surgeon, oncologist and radiologist. Somatostatin analogue such as octreotide is also useful in the treatment of carcinoid/neuroendocrine tumor as it inhibits the growth of the tumor and the release of the hormone.
The complication of neuroendocrine tumor may include bowel obstruction( fibrosis of primary tumor near the gut), electrolytes imbalance due to diarrhea, tricuspid stenosis , tricuspid regurgitation, pulmonary stenosis, right heart failure and metastases of the tumor.
Follow up treatment may include echocardiography and regular monitoring of the right sided congestive heart failure in case of unresectable carcinoid tumor. The purpose of this procedure to identify any endocardial fibrosis that may affect the valve, chordae and endocardium of the right side of the heart.
The mean survival rates is 5- 10 years and in some cases may range up to 20 years as the tumor is slow growing . Quality of life and survival will improve with early detection and treatment.
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