carcinoid syndrome
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Etiology
- syndrome resulting from release of neuroendocrine agents & other hormones from enterochromaffin cells (carcinoid)
- pulmonary carcinoid neoplasms or malignant carcinoid metastatic to the liver
Epidemiology
- peak incidence is in the 6th decade of life.
Pathology
- release neuroendocrine agents from tumor cells
- release of other hormones
- atypical carcinoid variants
- may be deficient in dopa-decarboxylase
- may secrete 5-hydroxytryptophan
- cardiac
- tricuspid valve & pulmonic valve thickening & stenosis
- excess serotonin can lead to fibrosis or the tricuspid valve & pulmonic valve
- endocardial fibrosis[5]
- tricuspid valve & pulmonic valve thickening & stenosis
- hepatomegaly[5]
- retroperitoneal fibrosis[5]
- pelvic fibrosis[5]
Clinical manifestations
- 5% of patients with carcinoid tumors manifest carcinoid syndrome
- carcinoid triad
- paraneoplastic manifestations
- associated with release neuroendocrine agents from tumor cells (see pathology)
- skin manifestations
- episodic skin flushing
- telangiectasias
- pellagra dermatosis (tryptophan depletion from 5-HT synthesis)
- cyanosis
- gastrointestinal manifestations
- hypotension
- pulmonary manifestations
- cardiac valvular dysfunction
- cardiac arrhythmias[5]
- small bowel obstruction may occur
Laboratory
- elevated 24 hour urine 5-hydroxy-indoleacetic acid (5-HIAA)
- acidify to pH of 2-3 with 10 mL of 6N HCl
- normal 2-8 mg 5-HIAA/24 hours
- false positives with foods high in tryptophan or serotonin: bananas, plantains, tomatoes, eggplant, pineapple, kiwi, walnuts, hickory note, pecans, avocados
- false negative with patients taking reserpine, salicylates, MAO inhibitors, phenothiazines, L-dopa
- eelevated blood 5-hydroxy-indoleacetic acid (5-HIAA)
- whole blood or platelet rich plasma
- collect in EDTA tube containing ascorbate
- most serotonin in blood is stored in platelets
- reference interval
- 50-200 ng/mL (whole blood)
- 125-500 mg/mL (platelet-rich plasma)
- 5-hydroxytryptophan in blood or urine
Radiology
- as indicated by signs/symptoms
- useful studies may include:
- abdominal CT
- endoscopy
- barium enema
- enteroclysis
- upper GI with small bowel follow through
- bone scans
- echocardiography
- octreotide scintigraphy
- octreotide binds type 2 somatostatin receptors
- type 2 somatostatin receptors expressed in large numbers by most carcinoid tumors
- identifies primary & metastatic tumor in 2/3 of patients
Management
- symptomatic treatment
- antihistamines (H1 & H2)
- phenoxybenzamine may inhibit release of bradykinin
- glucocorticoids may help relieve bronchospasm & wheezing
- octreotide inhibits tumor growth & hormone secretion by carcinoid cells
- successful treatment of underlying malignancy results in resolution of symptoms[4]
- chemotherapeutic protocols
- surgery
- prognosis
- carcinoid tumors
- 95% 5-year survival with local disease
- 65% 5-year survival with lymph node involvement
- 20% 5-year survival with liver metastases
- median survival is 2.5 years with carcinoid syndrome
- overall 18% 5 year survival without treatment
- overall 67% 5 year survival after introduction of octreotide
- carcinoid tumors
More general terms
Additional terms
References
- ↑ Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 533-35
- ↑ Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 55
- ↑ Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 585, 587
- ↑ Jump up to: 4.0 4.1 Medical Knowledge Self Assessment Program (MKSAP) 16, 17, 19. American College of Physicians, Philadelphia 2012, 2015, 2021
- ↑ Jump up to: 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Ahmad A (slide show) Carcinoid Tumors: Cancers in Slow Motion. Medscape. March 30, 2016 http://reference.medscape.com/features/slideshow/carcinoid-tumors