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Carcinoid tumor
Other names: Carcinoid
Multiple Carcinoid Tumors of the Small Bowel 2.jpg
Picture of a carcinoid tumor (center of image) that encroaches into the lumen of the small bowel. The prominent folds are plicae circulares, a characteristic of the small bowel.
SymptomsDigestive tract: Abdominal pain, vomiting, diarrhea[1]
Lungs: Trouble breathing, chest pain[1]
CausesGenerally unknown[1]
Risk factorsMultiple endocrine neoplasia type 1 (MEN1)[1]
Diagnostic methodLab tests, medical imaging, biopsy[1]
TreatmentSurgery, somatostatin analogs, targeted therapy, chemotherapy[1]
Frequency4 in 100,000 adults[1]

Carcinoid tumor, also known as carcinoid, are a type of tumor that develop from neuroendocrine tissue.[1] When the digestive tract is involve, symptoms may include abdominal pain, vomiting, or diarrhea.[1] When the lungs are involves, symptoms may include trouble breathing or chest pain.[1] Spread may results in a large liver.[2] One in ten cases involving the appendix presents with appendicitis.[2] About 5% of cases result in carcinoid syndrome.[2]

The cause is generally unknown.[1] They are associated with a genetic condition known as multiple endocrine neoplasia type 1 (MEN1).[1] It is a type of neuroendocrine tumor.[1] They develop from enterochromaffin cells, a type of neuroendocrine cell in the intestines.[2] They are generally slow-growing.[3] Diagnosis is based on lab tests, medical imaging, and biopsy.[1]

Treatment often involves surgery.[1] When surgery is not possible somatostatin analogs, targeted therapy, or chemotherapy may be used.[1] In young people who can have the lung tumor removed 5 year survival is greater than 90%.[1] They are estimated to affect about 4 in 100,000 adults.[1] They occur more commonly in adults than children.[1] About 10% of small bowel tumors are carcinoids, and most of these occur in the appendix and terminal ileum.[2]

Signs and symptoms

While most carcinoids are asymptomatic through the natural life and are discovered only upon surgery for unrelated reasons (so-called coincidental carcinoids), all carcinoids are considered to have malignant potential.

About 10% of carcinoids secrete excessive levels of a range of hormones, most notably serotonin (5-HT), causing:

  • Flushing (serotonin itself does not cause flushing). Potential causes of flushing in carcinoid syndrome include bradykinins, prostaglandins, tachykinins, substance P, and/or histamine, diarrhea, and heart problems. Because of serotonin's growth-promoting effect on cardiac myocytes, a serotonin-secreting carcinoid tumour may cause a tricuspid valve disease syndrome, due to the proliferation of myocytes onto the valve.[4]
  • Diarrhea
  • Wheezing
  • Abdominal cramping
  • Peripheral edema

The outflow of serotonin can cause a depletion of tryptophan leading to niacin deficiency. Niacin deficiency, also known as pellagra, is associated with dermatitis, dementia, and diarrhea.

This constellation of symptoms is called carcinoid syndrome or (if acute) carcinoid crisis. Occasionally, haemorrhage or the effects of tumor bulk are the presenting symptoms. The most common originating site of carcinoid is the small bowel, particularly the ileum; carcinoid tumors are the most common malignancy of the appendix. Carcinoid tumors may rarely arise from the ovary or thymus.[5]

They are most commonly found in the midgut at the level of the ileum or in the appendix. The next most commonly affected area is the respiratory tract, with 28% of all cases—per PAN-SEER data (1973–1999). The rectum is also a common site.


Primary site of a carcinoid cancer of gut

Carcinoid tumors are apudomas that arise from the enterochromaffin cells throughout the gut. Over two-thirds of carcinoid tumors are found in the gastrointestinal tract.[6]


Histopathology of a typical carcinoid tumor of the lung, with prominent rosettes.

Carcinoid tumors are also found in the lungs.

Other sites and metastases

Metastasis of carcinoid can lead to carcinoid syndrome. This is due to the over-production of many substances, including serotonin, which are released into the systemic circulation, and which can lead to symptoms of cutaneous flushing, diarrhea, bronchoconstriction, and right-sided cardiac valve disease. It is estimated that less than 6% of carcinoid patients will develop carcinoid syndrome, and of these, 50% will have cardiac involvement.[7]

Goblet cell carcinoid

This is considered to be a hybrid between an exocrine and endocrine tumor derived from crypt cells of the appendix. Histologically, it forms clusters of goblet cells containing mucin with a minor admixture of Paneth cells and endocrine cells. The growth pattern is distinctive: typically producing a concentric band of tumor nests interspersed among the muscle and stroma of the appendiceal wall extending up the shaft of the appendix. This makes the lesion difficult to suspect grossly and difficult to measure. Small tumor nests may be camouflaged amongst the muscle or in periappendiceal fat; cytokeratin preparations best demonstrate the tumor cells; mucin stains are also helpful in identifying them. They behave in a more aggressive manner than do classical appendiceal carcinoids. Spread is usually to regional lymph nodes, peritoneum, and particularly the ovary. They do not produce sufficient hormonal substances to cause carcinoid or other endocrine syndromes. In fact, they more closely resemble exocrine than endocrine tumors. The term 'crypt cell carcinoma' has been used for them, and though perhaps more accurate than considering them carcinoids, has not been a successful competitor.


Carcinoid syndrome involves multiple tumors in one out of five males. The incidence of gastric carcinoids is increased in achlorhydria, Hashimoto's thyroiditis, and pernicious anemia.


Surgery, if feasible, is the only curative therapy. If the tumor has metastasized (most commonly, to the liver) and is considered incurable, there are some promising treatment modalities, such as radiolabeled octreotide[8] (e.g. Lutetium (177Lu) DOTA-octreotate) or the radiopharmaceutical 131I-mIBG (meta iodo benzyl guanidine[8]) for arresting the growth of the tumors and prolonging survival in patients with liver metastases, though these are currently experimental.

Chemotherapy is of little benefit and is generally not indicated. Octreotide or lanreotide (somatostatin analogues) may decrease the secretory activity of the carcinoid, and may also have an anti-proliferative effect. Interferon treatment is also effective, and usually combined with somatostatin analogues.

As the metastatic potential of a coincidental carcinoid is probably low, the current recommendation is for follow up in 3 months with CT or MRI, labs for tumor markers such as serotonin, and a history and physical, with annual physicals thereafter.


They were first characterized in 1907 by Siegfried Oberndorfer, a German pathologist at the University of Munich, who coined the term karzinoide, or "carcinoma-like", to describe the unique feature of behaving like a benign tumor despite having a malignant appearance microscopically. The recognition of their endocrine-related properties was later described by Gosset and Masson in 1914, and these tumors are now known to arise from the enterochromaffin (EC) and enterochromaffin-like (ECL) cells of the gut. Some sources credit Otto Lubarsch with the discovery.[9]

In 2000, the World Health Organization redefined "carcinoid", but this new definition has not been accepted by all practitioners.[10] This has led to some complexity in distinguishing between carcinoid and other neuroendocrine tumors in the literature. According to the American Cancer Society, the 2000 WHO definition states:[10]

The WHO now divides these growths into neuroendocrine tumors and neuroendocrine cancers. Neuroendocrine tumors are growths that look benign but that might possibly be able to spread to other parts of the body. Neuroendocrine cancers are abnormal growths of neuroendocrine cells which can spread to other parts of the body.

Society and culture

  • Don Meyer, head coach emeritus of the Northern State University men's basketball team. Meyer was found to have carcinoid cancer following an automobile accident in September 2009.
  • Derrick Bell, professor and legal scholar, died of carcinoid cancer on October 5, 2011.


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 "Carcinoid Tumor - National Cancer Institute". 30 July 2020. Archived from the original on 2 December 2021. Retrieved 6 February 2022.
  2. 2.0 2.1 2.2 2.3 2.4 Jawad, Noor; Skinner, Charlotte (2020). "32. Gatroentrology". Kumar and Clark's Clinical Medicine (10th ed.). Elsevier. p. 1197. ISBN 978-0-7020-7870-5. Archived from the original on 2022-02-06. Retrieved 2022-02-06.
  3. Maroun J, Kocha W, Kvols L (April 2006). "Guidelines for the diagnosis and management of carcinoid tumors. Part 1: The gastrointestinal tract. A statement from a Canadian National Carcinoid Expert Group". Curr Oncol. 13 (2): 67–76. doi:10.3390/curroncol13020006. PMC 1891174. PMID 17576444.
  4. "Carcinoid Tumors and Syndrome". The Lecturio Medical Concept Library. Archived from the original on 9 July 2021. Retrieved 5 July 2021.
  5. Daffner KR, Sherman JC, Gilberto Gonzalez R, Hasserjian RP (2008). "Case 35-2008 — A 65-Year-Old Man with Confusion and Memory Loss". N Engl J Med. 359 (20): 2155–2164. doi:10.1056/NEJMcpc0804643. PMID 19005200.
  6. Modlin IM, Lye KD, Kidd M (February 2003). "A 5-decade analysis of 13,715 carcinoid tumors". Cancer. 97 (4): 934–59. doi:10.1002/cncr.11105. PMID 12569593.
  7. Fox DJ, Khattar RS (2004). "Carcinoid heart disease: presentation, diagnosis, and management". Heart. 90 (10): 1224–8. doi:10.1136/hrt.2004.040329. PMC 1768473. PMID 15367531.
  8. 8.0 8.1 "Medical Reviews". Archived from the original on 2015-11-15. Retrieved 2021-10-29.
  9. Kulke MH, Mayer RJ (March 1999). "Carcinoid tumors". N. Engl. J. Med. 340 (11): 858–68. doi:10.1056/NEJM199903183401107. PMID 10080850.
  10. 10.0 10.1 "ACS :: What Is a Gastrointestinal Carcinoid Tumor?". Archived from the original on 2016-11-05. Retrieved 2021-10-29.

External links

External resources