Gastrointestinal: Practice Question

A 52 year old patient has a clinical history of flushing, diarrhea, wheezing and a cardiac murmur found to have tricuspid insufficiency on echocardiogram. What is the most likely location of the lesion?
  1. Ileum
  2. Ovary
  3. Stomach
  4. Appendix
  5. Rectal
Show Answer and Explanations

Ileum — Correct answer

Correct. Carcinoid tumors are most commonly found in the GI tract followed by the pulmonary system. Within the GI tract they are found in decreasing order of frequency in the small intestine (mostly the ileum), rectum, appendix, colon and stomach. With increasing numbers of screening colonoscopy, the incidence of rectal carcinoids is on the rise, however, and may be greater than the incidence in the small intestine. Tumors of the midgut metastasizing to the liver are the most likely to cause carcinoid syndrome. The bronchi have a venous drainage not exposed to the liver circulation, so a bronchial carcinoid tumor can cause carcinoid syndrome, however tumors derived from tissues of the foregut and hindgut rarely produce carcinoid syndrome.

Ovary

Incorrect. Carcinoid tumors of the ovary are rare. When they occur, they tend to be a form of monodermal teratoma, and are the second most common form of monodermal teratoma, with struma ovarii (thyroid tissue) being the most common. About 1/3 of ovarian carcinoids produce carcinoid syndrome, and are able to do so because their venous drainage bypasses the liver.

Stomach

Incorrect. The stomach and ileum have some venous drainage that circumvents the liver circulation, but carcinoid tumors of the foregut (bronchus, thymus, and stomach) rarely produce carcinoid syndrome, and ileal carcinoids are more common than stomach (small intestine > rectum > appendix > colon > stomach)

Appendix

Incorrect. The appendix is a midgut (jejunum, ileum, ascending colon and appendix) location, and metastases to the liver can produce carcinoid syndrome. However, carcinoid tumors are more common in the ileum.

Rectal

Incorrect. The incidence is on the rise, however this is a less common location.

Summary

Summary: Carcinoid syndrome is most likely from metastases of a midgut (jejunum, ileum, ascending colon and appendix) tumor to the liver. Hindgut and foregut carcinoids rarely cause carcinoid syndrome. The frequency of carcinoids is GI > pulmonary. Within the GI tract, the frequency is small intestine > rectum > appendix > colon > stomach, but the incidence of rectal carcinoids is rising.
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