A lung carcinoid tumor is a type of growth that is composed of neuroendocrine cells. Under the microscope, these cells are similar to endocrine cells in the body that produce hormones. Carcinoid tumors may form in other organs of the body besides the lungs. In fact, only about 3 out of 10 carcinoid tumors are found in the lungs. Lung carcinoid tumors tend to grow slowly.
There are two types of lung carcinoid tumors: typical and atypical.
Another way to classify lung carcinoid tumors is by their location.
Central carcinoids are found in the large airways (breathing tubes) that connect the lungs to the center of the chest.
Peripheral carcinoids form closer to the edges of the lungs in the narrower air passages.
The cause of lung carcinoid tumors is unknown. They have not been demonstrated to be related to smoking, air pollutants, or other chemicals. However, there are factors that may put some people at an increased risk for developing one. Lung carcinoids are more likely to develop in whites than in people of other races and tend to be present in more women than men. People with a rare inherited disorder called multiple endocrine neoplasia type 1 (MEN1) are at somewhat higher risk for lung carcinoids.
How common are carcinoid tumors of the lung?
Lung carcinoid tumors are quite rare. There are about 4,500 new cases of lung carcinoid tumors diagnosed in the United States each year compared to almost 200,000 lung cancers. Carcinoid tumors are much more likely to develop in the digestive tract than in the lungs.
Many patients with lung carcinoid tumors do not have any symptoms. Often these types of tumors are found when a patient undergoes a test for another illness, such as a chest X-ray for a lung infection.
When symptoms are present, usually these symptoms include cough and wheezing. The cough might produce blood in the phlegm or sputum. If the tumor is large enough to block an air passage, a person might develop an infection called post-obstructive pneumonia which is caused by the backup of infected sputum behind the tumor.
Carcinoid syndrome is a condition related to overproduction of certain hormones by the tumors’ neuroendocrine cells. It is uncommon to have the carcinoid syndrome from a lung carcinoid tumor. Symptoms of carcinoid syndrome may include:
The symptoms of carcinoid syndrome may be caused by other disorders. It is important to see your doctor to find out the actual cause of the symptoms.
Your doctor will ask you about your medical history and any symptoms that you have. He or she will listen to your lungs and check your breathing. If your doctor suspects that there is a problem with your lungs, he or she will order more tests including:
Chest X-rays – a routine X ray that might indicate the presence of a lung carcinoid tumor.
Computed tomography scan (CT scan) — A CT scan yields images that provide a cross sectional view of the lungs and chest. Unlike regular X-rays, CT scans can detect very small lung tumors and pinpoint their exact location and aid in operative planning.
Depending on the test results, your doctor may order other tests to find out if the tumor is a carcinoid or some other form of lung growth.
Blood and urine tests—Abnormal levels of hormones or other substances linked with carcinoid tumors might be present in the blood or urine. Blood tests to measure the levels of serotonin or chromogranin-A might indicate the presence of a typical carcinoid. Urine tests can measure the level of 5-HIAA, a metabolite of serotonin. These tests are most helpful in the small percentage of people with lung carcinoid tumors who present with the carcinoid syndrome. In most others these tests will be normal.
Biopsy–A biopsy is a procedure in which a small sample of the tumor or growth is removed so that the cells can be examined under a microscope. Usually these can be reached and biopsied with a bronchoscope (small telescope inserted into the windpipe).
The method of treatment depends on the size of the tumor, its location, and a patient’s overall health. Surgery is the mainstay of treatment. Your surgeon will guide you in this decision making.
The main types of surgical treatment are
Prognosis for carcinoids is excellent. Typical carcinoids have better prognosis than atypical carcinoids. Survival rates are higher for people with lung carcinoids that are localized as opposed to tumors that have spread.
Your doctor will schedule regular follow-up visits for you after surgery with CAT scan imaging to be certain that the tumor does not recur (come back).