Where are carcinoid tumors most commonly located?

Carcinoid tumors are neuroendocrine tumors primarily arising from enterochromaffin cells, which are found throughout the gastrointestinal tract. While they can occur in various locations, the appendix is recognized as one of the most common sites for carcinoid tumors. Approximately half of all carcinoid tumors in the gastrointestinal tract are located in the appendix, particularly due to the high concentration of enterochromaffin cells in this area. The carcinoid tumors that develop in the appendix are often asymptomatic and may be discovered incidentally during appendectomy or imaging for another reason.

While carcinoid tumors can also be found in the stomach, liver, and intestines, they are less commonly diagnosed at these sites compared to the appendix. In the intestines, particularly the ileum, carcinoid tumors are indeed present but not as frequently as in the appendix. The liver may host metastatic carcinoid disease originating from other sites but is not a primary location of carcinoid tumor formation himself. Therefore, the appendix stands out as the most notable and common site for these tumors.