CARCINOID SYNDROME

I. Pathophysiology

  1. Tumors of enterochromaffin (neuroendocrine) cells
  2. Secrete serotonin (5-HT) and "tachykinins," e.g. substance P, occasionally others, e.g. ACTH, GHRH
  3. Primary tumor us. in ileum; can also be elsewhere in SI; bronchus, stomach, pancreas, thyroid, ovaries/testes
  4. Matastases us. to liver, also bone, lung, pancreas, etc.
  5. Us. don't cause sx before metastasis b/c of "first-pass" through liver metabolizes products of tumor

II. Clinical features

  1. Cutaneous flushing
  1. Us. head and neck
  2. Can be accompanied by tachycardia
  3. Us. no change in BP
  4. Can be precipitated by excitement, exertion, eating, EtOH
  1. Diarrhea
  1. Often explosive
  2. Accompanied by borborygmi and/or abd. cramping
  1. Cardiac vascular lesions
  1. Placquelike endocardial thickening R >> L
  2. Can result in valvular regurg. or stenosis
  1. Telangiectasias face/neck
  2. Bronchoconstriction (rare)
  3. Mechanical complications due to tumor itself, e.g. obstruction

III. Dx

  1. 24h urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of 5-HT
  2. >25mg/24h diagnostic
  3. Some foods, e.g. bananas, walnuts, contain 5-HT and can artificially increase 5-HIAA excretion
  4. MAOI's alter 5-HIAA determination? (ought to)

IV. Treatment

  1. Somatostatin analogues for symptomatic improvement of neuroendocrine effects (e.g. octreotide SQ; can cause hypoglycemia and steatorrhea; in some cases slows growth of tumor)
  2. Surgical excision/debulking (can be curative if tumor not metastatic, which is rare in symptomatic cases-see above)

V. Diff. dx of flushing

  1. Systemic mastocytosis
  2. EtOH ingestion
  3. Hypoestrogenic states in women
  4. Other neuroendocrine tumors (pheo, medullary Ca of thyroid, VIP-omas)

(Source: Cecil's textbook 20th ed.)