Carcinoid tumours

Carcinoid tumours are rare neuroendocrine lesions
Arise from amine precursor uptake and decarboxylation (APUD) cells
Approximately 1,000 are identified in the United Kingdom each year

Most primary tumours arise from the gastrointestinal tract
Commonest sites of primary tumours are appendix (30%), small bowel (20%)
Foregut tumours produce little 5HIAA - often produce other hormones (e.g. gastrin)
Midgut and hindgut tumours produce increased amounts of 5HIAA
When metastasis to liver these tumours produce the carcinoid syndrome

Clinical features

Carcinoid tumours produce vague right-sided abdominal discomfort
Symptoms have often been present for a number of years prior to diagnosis
Previous investigations have often been normal
Diagnosis is often only made after urgent surgery - usually due to obstruction

Picture provided by Jenny Wagener, Hawke's Bay District Hospital, New Zealand

In those with carcinoid syndrome symptoms include diarrhoea and flushing
Flushing affects face and neck lasting only several minutes
Often precipitated by alcohol or chocolate
May be associated with palpitations or hypotension
Examination is often normal
A right-sided abdominal mass or hepatomegaly may be present
Other features include telangiectasia, pellagra, tricuspid regurgitation.
Sclerotic bone secondaries occasionally occur

Investigation

Diagnosis confirmed by increased 24-hour urinary 5HIAA excretion
Plasma chromogranin A may be increased
Radiological investigations are rarely helpful
Ultrasound or CT may demonstrate an abdominal mass or liver secondaries
¹¹¹In - octreotide scintigraphy may identify primary or secondary tumour

Treatment

Diagnosis is often made after resection of primary tumour
Liver metastases are rarely amenable to hepatic resection
Conventional chemotherapy has poor response rate
Symptomatic carcinoid syndrome can often be palliated by:
- Somatostatin analogues (e.g. octreotide)
- Embolisation of hepatic metastases

Prognosis

Prognosis is better than for adenocarcinomas at similar sites
Median survival is 5 to 8 years
For surgically resectable tumours 10-year survival rates of more than 60% have been reported

Appendiceal carcinoid tumours

Most common tumour of the appendix
Found in 0.5% of appendicectomy specimens
Accounts for 85% of all appendiceal tumours
Usually an incidental finding found during appendicectomy
75% occur at the tip, 15% in the middle and 10% at the base of the appendix
80% are less than 1 cm in diameter
Only 5% are greater than 2 cm in diameter
Locoregional spread or metastases are rare especially if tumour is less than 2cm
Appendicectomy is adequate if tumour less than 1 cm
Right hemicolectomy needed if tumour greater than 1 cm
Prognosis is good with 5-year survival of 90-100%

Picture provided by Mr M Maniman, Royal Berkshire County Hospital, Reading, United Kingdom

Bibliography

Ganim R B, Norton J A. Recent advances in carcinoid pathogenesis, diagnosis and management. Surg Oncol 2000; 9: 173-179.

Onaitis M W, Kirshbom P M, Hayward T Z et al. Gastrointestinal carcinoids: characterization by site of origin and hormone production. Ann Surg 2000; 232: 549-556.

Pasieka J L. Carcinoid tumors. Surg Clin North Am 2009; 89: 1123-1137