Carcinoid syndrome overview

Overview
Carcinoid (also carcinoid tumour or carcinoid tumor) is slow-growing but often malignant type of neuroendocrine tumour, originating in the cells of the neuroendocrine system. Carcinoid tumours are apudomas that arise from the enterochromaffin cells throughout the gut. They are most commonly found in the foregut (35.6% cases) with lung, bronchus and trachea constituting 27.9% cases from where they rarely metastasise (except in case of pancreas). The next most common affected area is the small intestine especially the midgut (32.1% cases) with the highest proportion from ileum at 14.9% of all cases [as per the PAN-SEER data (1973-1999)]. In cases of metastases it can lead to carcinoid syndrome. This is due to the production of serotonin, which is released into the systemic circulation, which leads to symptoms of cutaneous flushing, diarrhea, bronchoconstriction and right-sided cardiac valve disease.

They were first characterized in 1907 by Siegfried Oberndorfer, a German pathologist at the University of Munich, who coined the term karzinoide, or "carcinoma-like", to describe the unique feature of behaving like a benign tumour despite having a malignant appearance microscopically. The recognition of their endocrine-related properties were later described by Gosset and Masson in 1914, and these tumours are now known to arise from the enterochromaffin (EC) and enterochromaffin-like (ECL) cells of the gut.