What is a lung carcinoid tumor?

A lung carcinoid tumor is a type of cancerous tumor made up of neuroendocrine cells. These cells are found throughout the body, including the lungs. They are similar to endocrine cells because both produce hormones or hormone-like substances. In other ways, they resemble nerve cells because both can secrete neurotransmitters.

Sometimes neuroendocrine cells grow too quickly and form a small tumor known as a carcinoid tumor. 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.

There are two types of lung carcinoid tumors: typical and atypical.

  • Typical carcinoids account for about 9 out of 10 lung carcinoids. They grow slowly and rarely spread beyond the lungs.
  • Atypical carcinoids are much rarer than typical lung carcinoids. They tend to grow faster than typical carcinoids. There is a greater chance that they will spread (metastasize) beyond the lungs. Another way to classify lung carcinoid tumors is by their location. Central carcinoids are found in the walls of the large airways of the lungs. Peripheral carcinoids form closer to the edges of the lungs in the smaller airways. Both central and peripheral carcinoids usually are typical carcinoids.

How common are carcinoid tumors of the lung?

Lung carcinoid tumors are quite rare, accounting for only 1% to 2% of all lung cancers. There are about 4,500 new cases of lung carcinoid tumors diagnosed in the United States each year. Carcinoid tumors are much more likely to develop in the digestive tract than in the lungs.

What causes lung carcinoid tumors?

The cause of lung carcinoid tumors is still unclear. They do not seem to be related to smoking, air pollutants, or other chemicals. However, there are factors that may put some people at an increased risk. 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.

What are the symptoms of lung carcinoid tumors?

About 25% or more of people with lung carcinoid tumors do not have any symptoms. Often these types of tumors are found when a patient undergoes diagnostic tests for another illness, such as a chest X-ray for a lung infection.

When symptoms are present, usually there is coughing or 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.

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:

  • Facial flushing (warmth) and redness
  • Wheezing or asthma-like symptoms
  • Shortness of breath
  • Weakness
  • High blood pressure
  • Weight gain
  • Increased amount of body and facial hair (hirsutism)

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.