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Carcinoid
Classification and external resources

Picture of a carcinoid tumour that encroaches into lumen of the small bowel (centre of image). Pathology specimen. The prominent folds are plicae circulares, a characteristic of small bowel.
ICD-10 C75.0;E34.0
ICD-9 259.2
ICD-O: M8240/3
OMIM 114900
DiseasesDB 2040
MedlinePlus 000347
eMedicine med/271
MeSH D002276

Carcinoid (also carcinoid tumour or carcinoid tumor) is a slow-growing[1] type of neuroendocrine tumour, originating in the cells of the neuroendocrine system.

Primary site of a carcinoid cancer of gut

In 2000, the World Health Organization redefined "carcinoid", but this new definition has not been accepted by all practitioners. [2] This has led to some complexity in distinguishing between carcinoid and neuroendocrine tumors in the literature.

Contents

Presentation

They are most commonly found in the midgut (75–87% cases). The next most common affected area is the respiratory tract with 28% cases of all cases — per PAN-SEER data (1973–1999).

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Gastrointestinal

Carcinoid tumours are apudomas that arise from the enterochromaffin cells throughout the gut.

Over two-thirds of carcinoid tumors are found in the gastrointestinal tract.[3]

Some sources list the appendix as the most common site. [4]

Other sites / metastases

In cases of metastases it can lead to carcinoid syndrome. This is due to the over-production of many substances, including serotonin, which is 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 10% of carcinoid patients will develop carcinoid syndrome.

Carcinoid tumors are also found in the lungs.

History

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 tumour despite having a malignant appearance microscopically. The recognition of their endocrine-related properties were later described by Gosset and Masson in 1914, and these tumours are now known to arise from the enterochromaffin (EC) and enterochromaffin-like (ECL) cells of the gut.

Some sources credit Lubarsch with the discovery.[5]

Symptoms

Most carcinoids are asymptomatic through the natural lifetime and are discovered only upon surgery for unrelated reasons; these are called coincidental carcinoids. But 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:

The outflow of serotonin can cause a depletion of tryptophan leading to niacin deficiency. Niacin deficiency, aka 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 tumour bulk are the presenting symptoms. The most common originating sites of carcinoid is the small bowel, particularly the ileum; carcinoid tumors are the most common malignancy of the appendix. Carcinoid tumours may rarely arise from the ovary or thymus.[6]

Treatment

Surgery, if feasible, is the only curative therapy. If the tumor has metastasized (most commonly, to the liver) and considered incurable, there are some promising treatment modalities, such as radiolabeled octreotide,, 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 (a somatostatin analogue) may decrease the secretory activity of the carcinoid.

While 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, like serotonin, and a history and physical, annual physicals thereafter.

Carcinoid tumors are the most common malignant tumor of the appendix, but they are most commonly associated with the small intestine, and they can also be found in the rectum and stomach. They are known to grow in the liver, but this finding is usually a manifestation of metastatic disease from a primary carcinoid occurring elsewhere in the body. They have a very slow growth rate compared to most malignant tumors.

Goblet Cell Carcinoid

This is considered to be a hybrid between an exocrine and endocrine tumour 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 tumour 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 tumour nests may be camouflaged amongst the muscle or in periappendiceal fat; cytokeratin preparations best demonstrate the tumour 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 the 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. The ICD-O code for goblet cell carcinoid is 8243/3.

See also

References

External links


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