Carcinoid tumours are a type of slow-growing cancer that can occur in various parts of the body, including the lungs, gastrointestinal tract, and appendix. These tumours can produce hormones and other substances that can cause a group of symptoms called carcinoid syndrome.

Carcinoid syndrome

• usually occurs when metastases are present in the liver and release serotonin into the systemic circulation (can result in dysregulated natural production of tryptophan, a precursor for both niacin B3 and seretonin, deficiency of niacin causing Pellagra)
• may also occur with lung carcinoid as mediators are not 'cleared' by the liver

PC:

• flushing (often earliest symptom)
• diarrhoea
• Abdominal pain
• bronchospasm and wheeze
• hypotension
• right heart valvular stenosis (left heart can be affected in bronchial carcinoid)
• pulmonary stenosis

Investigation

• urinary 5-HIAA (the major metabolite of 5-HT)
• plasma chromogranin A is raised in nearly all hindgut tumours and 80-90% of foregut and mifgut tumours