Small bowel (small intestine)
Other malignancies
Carcinoid syndrome

Author: Hanni Gulwani, M.D. (see Authors page)

Revised: 23 February 2018, last major update August 2012

Copyright: (c) 2003-2018, PathologyOutlines.com, Inc.

PubMed Search: Carcinoid syndrome[TI] small bowel

Cite this page: Gulwani, H. Carcinoid syndrome. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/smallbowelcarcinoidsyndrome.html. Accessed April 21st, 2018.
Definition / general
  • Occurs in 1% with carcinoid tumors, 20% with widespread metastases
  • Elevated levels of 5-hydroxyindoleacetic acid (5-HIAA), a metabolite, are found in blood and urine
  • Normally liver deactivates vasoactive amines (serotonin, histamine, bradykinin, others) released from carcinoid tumors
  • Clinical symptoms occur if liver metastases are present or if tumor venous blood flow bypasses the liver
Symptoms
  • Vasomotor disturbances (cutaneous flushes, cyanosis of face and anterior chest, intermittent hypertension), palpitations, intestinal hypermotility (nausea, vomiting, diarrhea, cramps)
  • Also asthmatic attacks with bronchospasm, fibrosclerosis of AV and tricuspid valves, elastotic sclerosis of mesenteric vessels causing ischemia, dermal sclerosis, hepatomegaly
Carcinoid heart disease
  • Right sided focal or diffuse plaques of thickened valvular or mural endocardium that may extend to the great veins, coronary sinus, pulmonary trunk and main pulmonary arteries
  • Tricuspid and pulmonic valves are usually affected by plaque formation
  • Left heart and left sided valves are less frequently affected
  • Endocardial fibrosis is a reaction to serotonin or kinin peptide exposure
  • Plaques are composed of fibroblasts, myofibroblasts and smooth muscle cells embedded in a collagenous matrix, covered by a layer of endothelium
  • No elastic tissue is present within the plaque