Gastrointestinal Carcinoid Tumour


Gastrointestinal carcinoid tumours make up over 70% of all carcinoid tumours and 40% of these are found in the appendix, with 20% found in the small bowel. The rectum is the third most common site for gastrointestinal carcinoid tumour.

Gastrointestinal carcinoids arises from the Kulschitzsky cells in the lining of the wall of the gut. They are also known as the argentaffin cells, due to their affinity for silver stains.

These tumours have distinct characteristics, in terms of their secretary functions. Fore gut carcinoid tumour (that is, up to the end of the duodenum), produces very little 5-hydroxy Indole Acetic Acid (5HIAA) and more of other hormones like gastrin, while mid gut and hind gut tumours (like those found in the appendix or rectum), produces large amounts of 5HIAA), thus these latter once are often more implicated in precipitating carcinoid syndrome once they metastasize to the liver.

Carcinoid tumour of the Appendix

Carcinoid tumour of the appendix is by far the most common form of gastrointestinal carcinoid tumour and carcinoid tumours in general. It accounts for about 85% of all tumours affecting the appendix.

It is estimated that for every 300 – 400 appendix removed, there is bound to be one case of carcinoid tumour. The statistics is even higher following autopsy, where it is reported that carcinoid tumour is seen in up to one out of every 150 appendix histology done following autopsy.

Carcinoid tumour of the appendix can affect any part of the appendix, especially the last one third. It is often found at the tip of the appendix (75% of cases) as discrete yellowish masses and rarely cause trouble.

They are described as invariable benign since they hardly metastasize, unlike tumours in carcinoid tumours in other sites. Appendicael carcinoid greater than 2 cm in diameter of course could metastasize.

“Carcinoid appendix” is often found accidentally following appendicectomy. Where they are the cause of problem, simple appendicectomy is often curative.

If the caecal wall is involved, removal of the appendix with part of the caecum or even the whole of the right colon may be warranted.

Survival rates after removal of carcinoid appendix is very good. Figures of 90 – 100% have been reported in the literatures.

Carcinoid tumour of the Small Intestines

Carcinoid tumour of the small intestines accounts for 20% of all carcinoid tumours. This gastrointesinal carcinoid tumour has variable incidence, depending on the part of the small intestine involved.

According to a Mayo Clinic series on gastrointestinal carcinoid tumours, of those affecting the small intestines, 2% occurs in the duodenum, 7% in the jejumeun, 89% in the ileum and 2% in Meckel’s diverticulum.

Small bowel tumours usually arise deep in the wall of the small intestines, and once they are 2cm or more, they often metastasize.

They are usually multiple tumours. Bone metastasis is rare with these tumours, unlike their hind gut and rectal counterparts which causes sclerotic bony deposits.

Problems with gastrointestinal carcinoid tumour, especially of the small bowel occur due to their causing extensive fibrosis and formation of adhesions. This causes the mesentery to contract, leading to the so-called “encasement phenomenon”, leading to bowel obstruction.

Metastasis to the liver causing stretch to the liver capsule is also another cause of trouble.

Unlike lung, thyroid, or thymus carcinoids, gastrointestinal carcinoid tumour is the chief cause of carcinoid syndrome. Tumours in other sites infrequently precipitate this well known syndrome associated with carcinoid tumours.

Other sites where carcinoid tumours are frequently found includes the lungs and liver. Please see these pages for:

Carcinoid Tumour of the Lungs

Tumour of the Liver

For further information on carcinoid tumours and their diagnosis, treatment and prognosis, please see the following pages:

Diagnosis of Gastrointestinal carcinoid Tumour and other carcinoids




Bailey & Love’s Short Practice of Surgery. 23 rd Edition.

C. D. Knox, C. D. Anderson, L. W. Lamps, R. B. Adkins, and C. W. PinsonLong-Term Survival after Resection for Primary Hepatic Carcinoid TumorAnn. Surg. Oncol., December 1, 2003; 10(10): 1171 - 1175.

Lung Cancer: Principles and Practiceedited by Harvey I Pass, David P Carbone, John D Minna, Andrew T Turrisi, David H Johnson

General Thoracic Surgery By Thomas W Shields, Joseph Locicero, Ronald B Ponn, Valerie W Rusch

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