Malignant Carcinoid Syndrome Clinical Presentation

Updated: Aug 03, 2021
  • Author: Luigi Santacroce, MD; Chief Editor: N Joseph Espat, MD, MS, FACS  more...
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Carcinoid tumors grow slowly, and symptoms may not occur for several years, if at all. When symptoms do develop, they are ill defined and may be neglected for a long time before being properly diagnosed. In some cases, carcinoid tumors present as acute appendicitis or chronic pain in the lower right abdominal quadrant. For this reason, the condition is frequently misdiagnosed as irritable bowel syndrome. [21] Alcohol intolerance and weight loss also may be associated manifestations.

Severity of symptoms varies. Onset of symptoms may be spontaneous or may be precipitated by certain foods and beverages (eg, alcohol), pharmacologic agents, and physical or emotional stress.

Diarrhea is common, as is flushing of the face and neck. [22] These manifestations result from tumoral hormone production; however, even if a carcinoid tumor produces these molecules, some patients do not experience any symptoms.

Flushing is a phenomenon in which transient vasodilation causes reddening of the face, head, neck, and the upper chest and epigastric areas. [23] Flushing is the most frequent symptom and may be brief (eg, 2-5 min) or may last for several hours, usually in later disease stages.

Flushing may be accompanied by tachycardia, while the blood pressure usually falls or does not change. Malignant carcinoid syndrome is not a cause of sustained hypertension, and a rise in blood pressure during flushing is rare.

In addition to cutaneous vasodilation, some patients also develop telangiectasia, primarily on the face and neck, which is most marked in the malar area.

Right heart problems may develop because the tricuspid valve is stenosed by serotonin action, causing shortness of breath after a few years. However, carcinoid heart disease may produce no symptoms or clinical signs; for that reason, some authors have advocated screening with echocardiography in all patients with carcinoid syndrome. [24]

Other common problems include the following:

  • Asthma
  • Wheezing
  • Dyspnea
  • Palpitations
  • Low blood pressure
  • Fatigue
  • Dizziness
  • Asthenia

Uncommon symptoms include the following:

  • Myopathy
  • Arthritis
  • Arthralgias
  • Irritability, aggression, and lack of impulse control; these have been linked with low levels of plasma tryptophan and presumably with low brain serotonin [16]

Intestinal obstruction may result from the primary tumor or from the sclerosing reaction in the surrounding mesentery. Necrosis of hepatic tumor masses may produce a typical acute syndrome with fever, abdominal pain, tenderness, and leukocytosis.



Wheezing, facial telangiectasis with cyanosis and edema, pallor, flushing, macular erythema, and periorbital edema, accompanied by hepatomegaly, pellagralike skin lesions, steatorrhea, and chronic diarrhea, all suggest the diagnosis.

During chest examination, a pulmonary systolic and diastolic heart murmur may be heard if cardiac involvement is present. Cardiac involvement is associated with pulmonic valve stenosis and/or tricuspid insufficiency. [25]

Bronchospasms, which cause asthmalike attacks, are generally most pronounced during flushing attacks. Bronchospasms are a less common sign of malignant carcinoid syndrome but may be severe.

Any sign of niacin deficiency (pellagra) must be investigated carefully. [26]

Debilitating diarrhea is common and may have a secretory component.

  • As many as 20 episodes of diarrhea per day are possible and cause marked debilitation due to fluid, electrolyte, and protein depletion.

  • The diarrhea persists with fasting, fails to disappear when the patient is fed intravenously, and is usually accompanied by flushing; however, diarrhea occurs alone in approximately 15% of patients.

  • Abdominal borborygmi and cramping or pain may be present. When severe, malabsorption may occur and may even cause death.

  • Primary tumors seldom cause gastrointestinal bleeding.

Hepatomegaly from metastases is usually present, but extensive metastatic liver involvement may occur before liver function test results become abnormal.

Carcinoid heart disease is reported in approximately 50-60% of all patients with malignant carcinoid syndrome and is severe in approximately 25%.

  • Carcinoid heart disease occurs primarily on the right side of the heart but may involve the left side to a minimal degree.

  • Fibrous deposits adhering to the surface of the valvular endocardium may occur as part of this condition. [27]

  • Thickening of the endocardium of the cardiac chambers and papillary muscles and thickening and deformation of the valve cusps and chordae tendineae can lead to heart failure, influencing valvular function and causing regurgitation, stenosis, or combined functional lesions.

  • The tricuspid valve is affected most commonly.