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Lung carcinoid tumors (also known as lung carcinoids) are a type of lung cancer. Cancer starts when cells begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas. (To learn more about how cancers start and spread, see What Is Cancer?)
Lung carcinoid tumors are uncommon and tend to grow slower than other types of lung cancers.
Lung carcinoid tumors start in neuroendocrine cells, a special kind of cell found in the lungs. Neuroendocrine cells are also found in other areas of the body, but only cancers that form from neuroendocrine cells in the lungs are called lung carcinoid tumors.
Neuroendocrine cells are like nerve cells in some way, and like hormone-making endocrine cells in other ways. They make hormones like adrenaline and similar substances. Cells in this system don't form actual organs. Instead they are scattered throughout the body in organs like the lungs, stomach, and intestines.
Neuroendocrine cells in the lungs can have several different functions. They may:
Lung carcinoid tumors start in the lungs – 2 sponge-like organs in your chest. Their main functions are to take in oxygen and get rid of carbon dioxide.
Your right lung has 3 sections, called lobes. The left lung has 2 lobes. It is smaller because the heart takes up room on that side of the body.
When you breathe in, air enters through your mouth and nose and goes into your lungs through the trachea (windpipe). The trachea divides into tubes called the bronchi (singular, bronchus), which enter the lungs and divide into smaller branches called the bronchioles. At the end of the bronchioles are tiny air sacs known as alveoli. Many tiny blood vessels run through the alveoli. They absorb oxygen from the inhaled air into your bloodstream and pass carbon dioxide (a waste product from the body) into the alveoli where it is expelled from the body when you exhale.
A thin lining called the pleura surrounds the lungs. The pleura protects your lungs and helps them slide back and forth as they expand and contract during breathing. The space inside the chest that contains the lungs is called the pleural space (or pleural cavity).
Below the lungs, a thin, dome-shaped muscle called the diaphragm separates the chest from the abdomen. When you breathe, the diaphragm moves up and down, forcing air in and out of the lungs.
Carcinoid tumors are sometimes classified by where they form in the lung. The tumor’s location is important because it can affect which symptoms a patient has and how the tumor is treated.
Lung carcinoid tumors are a type of neuroendocrine tumor. Neuroendocrine tumors are more common in the digestive system (see Gastrointestinal Carcinoid Tumors and Pancreatic Cancer), but the second most common place is in the lungs.
There are 2 types of lung carcinoid tumors:
In addition to lung carcinoid tumors, there are other types of neuroendocrine tumors that start in the lungs: small cell lung cancer and large cell neuroendocrine carcinoma, which is a type of non-small cell lung cancer. These lung cancers are treated differently, so it's important to know exactly what type you have.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
Hilal T. Current understanding and approach to well differentiated lung neuroendocrine tumors: an update on classification and management. Therapeutic Advances in Medical Oncology. 2017;9(3):189-199. doi:10.1177/1758834016678149.
Derks JL, van Suylen RJ, Thunnissen E, et al. Chemotherapy for pulmonary large cell neuroendocrine carcinomas: does the regimen matter? The European Respiratory Journal. 2017;49(6):1601838. doi:10.1183/13993003.01838-2016.
Horn L, Eisenberg R, Guis D et al. Chapter 72: Cancer of the Lung – Non-small Cell Lung Cancer and Small Cell Lung. In: Niederhuber JE, Armitage JO, Dorshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 5th ed. Philadelphia, Pa. Elsevier: 2014.
Melosky B. Low Grade Neuroendocrine Tumors of the Lung. Frontiers in Oncology. 2017;7:119. doi:10.3389/fonc.2017.00119.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Neuroendocrine and Adrenal Tumors. V.2.2018. Accessed at https://www.nccn.org/professionals/physician_gls/pdf/neuroendocrine.pdf on July 11, 2018.
Pelosi G, Sonzogni A, Harari S, et al. Classification of pulmonary neuroendocrine tumors: new insights. Translational Lung Cancer Research. 2017;6(5):513-529. doi:10.21037/tlcr.2017.09.04.
Last Revised: August 27, 2018
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