Natural history of intestinal carcinoids.

Historically, carcinoids are a morphologically distinct class of rare intestinal tumours that behave less aggressively than the more common intestinal adenocarcinomas. Some authors restrict the term carcinoid to intestinal endocrine tumours, and others include a large variety of neuroendocrine tumours. Within the gastrointestinal tract, carcinoids are most commonly found in the appendix, followed by the distal small bowel, rectum and stomach. In the vast majority of cases, the carcinoid syndrome is associated with carcinoid tumours of the small intestine that have metastasised to the liver. Episodic flushing and diarrhoea are the most common initial symptoms. Metastatic disease may require no treatment for months or even years in the patient whose symptoms are not seriously interfering with quality of life and if the tumour is not exhibiting a biologically aggressive growth pattern.