A carcinoid tumor is a type of neuroendocrine tumor which can occur in number of locations.
Carcinoid tumors arise from endocrine amine precursor uptake and decarboxylation (APUD) cells that can be found throughout the gastrointestinal tract as well as other organs (e.g. lung). In general they are slow growing tumors, but are nevertheless capable of metastasis.
The gastrointestinal tract accounts for ~ 85% carcinoid tumors while carcinoid accounts for ~ 2% of gastrointestinal tract tumors.
- appendiceal carcinoid - the appendix accounts for ~ 50% of all carcinoid tumors
- small bowel carcinoid - the terminal ileum accounts for ~ 90% of all small bowel carcinoid tumors