Carcinoid Tumors 

Carcinoid  tumors are noncancerous (benign) or cancerous (malignant) growths  that sometimes produce excessive amounts  of hormonelike substances, resulting  in the carcinoid syndrome. 

• People with carcinoid tumors may have cramping pain  and changes  in bowel movements. 
• People  with carcinoid syndrome usually have  flushing and sometimes diarrhea. 
• Doctors measure  the amount  of a serotonin byproduct in a person's urine.
• Imaging tests are needed to determine tumor location. 
• Sometimes  tumors are removed surgically. 
• People may need to take drugs to control symptoms. 

Carcinoid tumors usually originate in hormone-producing cells that line  the small intestine or  other cells of the digestive tract. They can also occur  in the pancreas, testes, ovaries, or lungs. Carcinoid tumors can produce an excess  of hormonelike substances, such as serotonin, bradykinin, histamine,  and prostaglandins. Excess levels of these substances can sometimes result in  a diverse set of symptoms called carcinoid syndrome. Carcinoid tumors use the amino acid tryptophan  to produce the excess serotonin. Because tryptophan is normally used to make niacin (vitamin B3), people may develop a niacin deficiency, causing the disease pellagra. 

When carcinoid tumors occur in the digestive tract  or pancreas, the substances  they produce  are released into a blood vessel that flows directly  to the liver (portal vein), where enzymes destroy them. Therefore, carcinoid tumors that originate  in the digestive tract generally do not produce symptoms unless  the tumors have spread to  the liver.

If  the tumors have spread to  the liver,  the liver  is unable to process  the substances before they begin circulating throughout the body. Depending on  which substances are being released by the tumors, the person  will have  the various symptoms of carcinoid syndrome.  Carcinoid tumors of the lungs, testes, and ovaries also  cause symptoms because the substances they produce bypass the liver  and circulate widely in the bloodstream. 

Symptoms 

Most people with carcinoid  tumors have symptoms similar to those of other intestinal tumors, mainly cramping pain  and changes in bowel movements as a result of obstruction. 

Carcinoid Syndrome:  Fewer than 10% of people with carcinoid tumors develop symptoms of carcinoid syndrome, although this percentage varies depending on where  the tumor is located. Uncomfortable flushing, typically  of the head and neck, is the  most common and often the earliest symptom  of carcinoid syndrome. Flushing, the result of blood vessel dilation, is often triggered by emotions, by eating,  or by drinking alcohol or hot liquids. The flushing may be followed by periods when the skin is bluish (cyanosis). Excessive contraction  of the intestine may result in abdominal cramping  and diarrhea. The intestine  may not be able  to absorb nutrients properly, resulting in undernutrition and fatty, foul-smelling stools. 

Heart damage may occur, resulting in swelling  of the feet  and legs (edema). Wheezing  and shortness of breath may result from obstructed airflow in  the lungs. Some people with  carcinoid syndrome lose interest in sex, and some men have erectile dysfunction. 

Diagnosis
When symptoms lead a doctor to suspect a carcinoid tumor,  the diagnosis can  often be confirmed by measuring  the amount  of 5-hydroxyindoleacetic acid (5-HIAA)—one  of the chemical by-products of serotonin—in the person's urine, which is collected over  a 24-hour period. For at least 3 days before undergoing this test, the person refrains from eating foods that  are rich in serotonin—bananas, tomatoes, plums, avocados, pineapples, eggplants,  and walnuts. Certain drugs, including guaifenesin (found in many cough syrups), methocarbamol (a muscle relaxant), and phenothiazines (antipsychotics), also interfere with test results. 

Different tests are used to locate  carcinoid tumors. These tests include computed tomography (CT), magnetic resonance imaging (MRI),  and arteriography. Sometimes exploratory surgery is needed to locate  the tumor.

Radionuclide scanning is another useful test.  Most carcinoid tumors have receptors for  the hormone somatostatin. Doctors can therefore inject a radioactive form  of somatostatin into  the blood and use radionuclide scanning to locate a carcinoid tumor and determine if it has spread. About 90%  of tumors can be located using this technique. MRI or CT can be helpful in confirming whether the tumor has spread to the liver. 

Treatment 

When a  carcinoid tumor  is restricted  to a specific area, such as the appendix, small intestine, rectum, or lungs, surgical removal may cure the disease. If the tumor  has spread  to the liver, surgery rarely cures the disease but may help relieve symptoms. The  tumors grow so slowly that even people whose  tumors have  spread often survive for 10  to 15 years. 

Neither radiation therapy nor chemotherapy is effective  in curing carcinoid tumors. However, combinations  of certain chemotherapy drugs ( streptozocin with fluorouracil and sometimes doxorubicin) may relieve symptoms. A drug called octreotide can also relieve symptoms, and tamoxifen  and interferon-alpha may reduce  the tumor's growth. Phenothiazines, cimetidine,  and phentolamine are used  to control flushing in people with carcinoid syndrome. Prednisone  is sometimes given to people with carcinoid tumors of  the lung who have episodes of severe flushing. Diarrhea may be controlled with codeine, tincture of opium, diphenoxylate, or cyproheptadine. Pellagra may be prevented by drugs that block  the production  of serotonin, such  as methyldopa and phenoxybenzamine.