Small Intestine: Carcinoid Tumor

Pathophysiology

• Well-Differentiated Neuroendocrine Tumor Arising from Gastrointestinal Enterochromaffin (Kulchitsky) Cells
• Produce:
  • Serotonin (Metabolized to 5-HIAA)
  • Kallikrein
  • Histamine
  • Tachykinins
  • Prostaglandin

Location

• Most Common Site: Small Intestine (50%) < Rectum < Appendix < Colon < Stomach
  • Most Common in Ileum
  • *Past Believed That the Appendix Was Most Common
• Most Common Primary Small Intestine Tumor
• Gastric Tumor Types (If in Stomach)
  • Type I: Associated with Chronic Atrophic Gastritis & Pernicious Anemia
    • Most Common Gastric Subtype (70-80%)
    • Grow Slowly
  • Type II: Associated with Gastrinoma & Possibly MEN-I
    • Intermediate Growth
  • Type III: Sporadic
    • Aggressive

Presentation

• Most Common Presenting Sx: Abdominal Pain
• Carcinoid Syndrome
  • Infrequently Encountered
  • Occurs Once Tumor Metastasizes to Liver or Retroperitoneum
    • Serotonin Cleared in Liver & Lung by Monoamine Oxidase if Only Produced by GI Tract
  • Sx:
    • Flushing (From Kallikrein)
      • Clinical Hallmark of Carcinoid Syndrome (85%)
    • Diarrhea (From Serotonin)
    • Bronchoconstriction (From Bradykinin)
    • Right Heart Valve Lesions & Tricuspid Insufficiency
    • Venous Telangiectasia (From Prolonged Vasodilation of Face)
• Carcinoid Crisis
  • The Release of an Overwhelming Amount of Hormone from the Tumor
  • Causes Hemodynamic Instability & Symptoms of Carcinoid Syndrome
  • Triggers:
    • Anesthesia Induction
    • Tumor Manipulation (Biopsy or Manual Palpation)
    • Invasive Procedures
    • Less Common:
      • Chemotherapy
      • Hepatic Artery Embolization

Prognosis

• 25% Have More Than One Small Bowel Tumor at Diagnosis
• 40-80% Have Spread to the Mesentery with Nodal Metastases at Diagnosis
• 2/3 Have Spread by Time of Dx (Local or Systemic)

Diagnosis

• CT of Mesenteric Masses Classically Show a Spiculated Mass with Calcification & Desmoplastic Reaction
• Detect:
  • Urinary 5-HIAA
    • Best Initial Test
    • Low Sensitivity if Non-Functioning
  • Chromogranin A Level
    • Can Also Detect Non-Functioning
    • Low Specificity (Not for Diagnosis)
    • Use: Progression, Response & Recurrence
• Localize:
  • Octreotide Scan
  • 68 Ga-DOTATATE PET/CT Scan – Generally Preferred if Available
    • Superior Image Quality with Greater Patient Convenience (Octreotide Scan May Require Repeat Images the Next Day)

Treatment

• Primary Tx: Resection
  • If Unresectable: Chemo (Streptozocin & 5FU) & Octreotide
• Liver Mets: Resect if Able
  • Contraindications:
    • Diffuse Bilobar Involvement
    • Compromised Liver Function
    • Extrahepatic Metastases
    • Presence of Poorly-Differentiated Carcinoma
  • Consider Preoperative Hepatic Artery Embolization
  • Very Good Survival Rates Even with Extensive Liver Mets
• Symptomatic Tx:
  • Flushing: α-Blockers
  • Other Symptoms: Octreotide
• Carcinoid Crisis: Octreotide