carcinoid tumor
Summary
Carcinoid tumors are well-differentiated neuroendocrine tumors arising from enterochromaffin cells, most commonly in the GI tract and lungs. They secrete serotonin and other vasoactive substances, potentially causing carcinoid syndrome when metastatic to the liver.
Detail
Carcinoid tumors originate from enterochromaffin (Kulchitsky) cells and are part of the neuroendocrine tumor spectrum. The most common locations are the appendix (40%), small intestine (30%), and rectum (15%), with bronchial carcinoids comprising most pulmonary cases. These tumors secrete serotonin, histamine, and other vasoactive peptides. Carcinoid syndrome occurs in <10% of patients, typically when liver metastases are present, allowing vasoactive substances to bypass hepatic metabolism and reach systemic circulation. The syndrome presents with episodic flushing, diarrhea, bronchospasm, and right-sided heart disease (tricuspid regurgitation/stenosis, pulmonary stenosis). Diagnosis involves measuring 24-hour urine 5-HIAA (serotonin metabolite) and serum chromogranin A. Imaging includes CT/MRI and octreotide scintigraphy. Treatment depends on location and stage: surgical resection for localized disease, octreotide for symptom control, and various therapies for metastatic disease including somatostatin analogs, targeted therapy, and liver-directed treatments.
Sources
- Robbins and Cotran Pathologic Basis of Disease
- Harrison's Principles of Internal Medicine
- First Aid for the USMLE Step 1
- UpToDate: Carcinoid tumors
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.