Epidemiology

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  6.2 per 100,000 and rising. Found most commonly in the seventh decade of life, in males, in Caucasians, and at an advanced stage. Midgut carcinoids are more prevalent than foregut or hindgut.

  
  
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  Even when small, these tumors may cause an intense local desmoplastic response and may metastasize.

  
  

  Carcinoid tumors are the second most prevalent gastrointestinal tumor.

Pathology

Arise from the neuroendocrine cells of Kulchitsky. Grading for aggressiveness is the same as for PNETs (primitive neuroectodermal tumors). Most (75%) arise in the small bowel followed in order by rectum, lung, and bronchus. ¹

Usually, the tumor is indolent with 5-year survival in 52–77% of cases. ²

Staging

These tumors parallel that of colon carcinoma.

Diagnosis

Elevated 24-hour urine 5-HIAA (5-Hydroxyindoleacetic acid).

Elevated serum chromogranin A.

Computed tomography or magnetic resonance imaging demonstrating a mass in the small bowel or colon, with or without liver metastases.

Somatostatin receptor-based scintigraphy (OctreoScan).

Carcinoid syndrome

It usually occurs with midgut carcinoid tumor metastases to the liver or to organs that do not supply the portal vein, for example, ovary, due to release of tumor-derived factors such as serotonin, dopamine, tachykinins, histamine, and prostaglandins.

Some of the symptoms include diarrhea, flushing, wheezing, carcinoid heart disease, episodic hypertension. Flushing is most common (94% of patients) and occurs in the upper chest, head, and neck. It may be provoked by alcohol, nuts, cheese, and stress. Diarrhea is present in 80% of cases. Heart disease involves carcinoid plaques in the tricuspid and pulmonary valves due to the serotonin released by the tumor in the liver. Valve lesions may lead to right-sided heart failure.

All patients undergoing any procedure should be blocked with octreotide (100–500 µg) intravenously 1 to 2 hours before the procedure. ³ Patients who do not respond to somatostatin may benefit from interferon a. ⁴