About Carcinoid Tumors
The neuroendocrine system is made up of cells that "connect" the nervous system and the endocrine system. Neuroendocrine cells release hormones (sometimes called peptides) into the circulatory system in response to a stimulus received from the nervous system. These specialized cells are scattered throughout the organs in the body and are the cells that give rise to neuroendocrine tumors.
There are many types of tumors that arise from the neuroendocrine system of which carcinoid tumors are the most common. Carcinoid tumors were initially identified in 1888 and were thought to clinically and histologically (cellular appearance under a microscope) resemble carcinoma cells (highly malignant cancer cells) but behave in a more benign fashion than true cancer cells. Over the years it became clear that carcinoid tumors can be quite aggressive, can metastasize, and can cause carcinoid syndrome. Most carcinoid tumors are now known to be slow growing malignant tumors that have their own specific biological and clinical characteristics.
Carcinoid tumors share some properties with other cancer cells such as uncontrolled, overproduction of the cells that results in tumor formation and malignant potential. However, carcinoid tumor cells are distinguished from most other types of tumors in that they secrete various hormone-like substances (e.g., serotonin, noradrenalin, histamines) which may cause symptoms throughout the body rather than symptoms localized to the organ where the tumor originates.
Carcinoid tumors can appear anywhere neuroendocrine cells are present including the gastrointestinal (GI) tract, lungs, ovaries, pancreas, appendix, small and large intestine, testes, and rectum. The location of origin of carcinoid tumors is divided into three categories:
- Foregut Carcinoid Tumors - These tumors originate in the lungs, thymic gland, pancreas, stomach, and duodenum (lung and stomach are most common locations)
- Midgut Carcinoid Tumors - These tumors originate in the small intestines, appendix, and right colon (small intestines and appendix are most common locations)
- Hindgut Carcinoid Tumors - These tumors originate in the large intestines, specifically in the transverse colon, descending colon, and rectum.
According to the American Society of Clinical Oncology (ASCO), approximately 11,500 people in the United States are diagnosed each year with a carcinoid tumor. About 66% of all carcinoid tumors develop in the gastrointestinal tract. If the tumor can be surgically removed and has not spread outside of the organ where it started, the 5-year relative survival rate for gastrointestinal carcinoid tumors is in the range of 70% to 90%. The next most common site for the development of carcinoid tumors is in the lungs. Approximately 3,000 new cases of lung carcinoid tumors are diagnosed in the United States each year.
Carcinoid tumors are in general quite rare and occur in approximately 2.5-5 per 100,000 people. It is probable that more people may actually have carcinoid tumors but because carcinoids are often asymptomatic, an individual may never know that a carcinoid has developed. Consequently, the majority of cases are discovered incidentally during a routing medical examination. The age at diagnosis varies somewhat among specific tumor locations but typically, most people diagnosed with a carcinoid tumor are in their 50s.
Carcinoid tumors are slow-growing tumors and most do not cause symptoms until they interfere with daily function or metastasize. Symptoms are often associated with the site of tumor origin and reflect the tumor obstructing organs involved in normal body function but may be less specific if related to carcinoid syndrome.
Carcinoid syndrome describes a combination of symptoms that result from hormones or hormone-like substances, (e.g., serotonin, gastrin, ACTH) that are produced by some carcinoid tumors.
The release of these hormone-like substances into the bloodstream causes symptoms of carcinoid syndrome that include:
- Flushing
- Diarrhea
- Abdominal pain
- Wheezing
- Carcinoid heart disease
- Carcinoid crisis - when all of the above symptoms occur at the same time.
The optimal management of patients with carcinoid tumors involves a multidisciplinary team of health care providers including an oncologist, gastroenterologist, surgeon, radiologist and nuclear medicine specialist.
The goals of treatment for carcinoid treatment include:
- Surgical removal of the tumor
- Managing and reducing symptoms
- Managing metastatic disease
The prognosis (outlook or chance of recovery) for patients with carcinoid tumors is based primarily on size of the tumor and the degree to which it has spread and invaded other tissues in the body. In general, because carcinoid tumors grow and spread slowly, they often are discovered at an early stage thereby improving the chance of a successful outcome. In addition, the wide variety of effective treatments that is available for patients even with more aggressive carcinoids that have metastasized continues to improve the prognosis for carcinoid tumors.
The Medifocus Guidebook on Carcinoid Tumors is a unique, comprehensive patient education resource that contains vital information about Carcinoid Tumors that you won't find anywhere else in a single resource. The Guidebook will answer many of your questions about this condition that your healthcare provider may not have the time to answer. To learn more about the Guidebook, please click here
