Carcinoid syndrome is a pattern of symptoms that occurs in people who have carcinoid tumours. The symptoms are caused by hormones and chemicals produced by the carcinoid tumour and, in many cases, these symptoms are actually worse than the effects of the growth of the tumour itself.
Carcinoid tumours were first identified in Europe in the mid-1800s as a specific, distinct type of growth. The name carcinoid was first used in 1907 to classify them as a type of tumour that fit midway between malignant (cancerous) tumours and ones that were benign (non-malignant).
Carcinoid tumours can be widely distributed throughout the body, but are usually found in the digestive system (50% of cases) or lung (30% of cases). In children, carcinoid tumours are usually found in the appendix. Once the appendix is removed, the cancer is usually cured.
Carcinoid tumours produce too much of certain chemicals and hormones and this can cause reactions in the body. One common chemical produced by carcinoid tumours is a hormone called serotonin. This hormone makes the blood vessels dilate (widen) and causes increased blood clotting, intestinal secretions, and motility (causing diarrhea).
Carcinoid tumours are rare, with 1 to 2 cases in every 100,000 people. It makes up less than 1% of all cancers.