CARCINOID TUMOURS

Question 1

What are carcinoid tumours and what do they secrete? Where are they typically found?

Answer 1

Neuroendocrine tumours

Secrete serotonin

Found in GI tract, pancreas, lungs; small intestine most common place

Question 2

What are the two main presenting complaints of carcinoid tumours?

Answer 2

Diarrhoea and flushing

carcinoid tumour + symptoms = carcinoid syndrome

Question 3

Which organs metabolise and inactivate the serotonin produced by carcinoid tumours?

Answer 3

Liver and lungs

Question 4

If serotonin is inactivated by the liver and lungs, how do carcinoid tumours result in a carcinoid syndrome?

Answer 4

If carcinoid tumour metastasises to liver then serotonin produced can be released into bloodstream without being metabolised → carcinoid syndrome

Question 5

How do carcinoid tumours affect heart valves? Explain why one side of heart is more affected than other

Answer 5

Serotonin increases fibroblast growth and fibrogenesis particularly of pulmonary and tricuspid valves. Right side affected more due to deactivation of serotonin in lungs

Question 6

What can carcinoid tumours do to tryptophan metabolism?

Answer 6

Alter tryptophan metabolism: normally 1% is used to synthesise serotonin

In carcinoid syndrome around 70% of tryptophan is used to synthesise serotonin. Tryptophan is important in synthesis of niacin (vitamin B3) → deficiency causes pellagra

Question 7

In a patient with diarrhoea and flushing, if you suspect a carcinoid syndrome how will you diagnose?

Answer 7

24-hour urine sample needed for diagnosis: measures 5-hydroxyindoleacetic acid (5-HIAA)

→ metabolite of serotonin breakdown, will be elevated in people with carcinoid tumours

Question 8

What are the three main treatment options for carcinoid syndrome?

Answer 8

• Surgical excision of tumour
• Hepatic resection: often improves symptoms even when carcinoid tumour remains in GIT
• Octreotide: somatostatin analogue ⇒ somatostatin receptors found on many carcinoid tumours so administration will inhibit release of bioactive amines such as serotonin

Question 9

In someone with a carcinoid tumour where would you expect to hear a murmur if tricuspid valve is affected? Where would you expect to hear it if pulmonary valve is affected?

Answer 9

• Tricuspid: 4th to 5th intercostal space over left sternal border
• Pulmonary: 2nd intercostal space just lateral to left sternum