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Small Bowel Carcinoid Tumor

Clinical Subject Page

Small Bowel Carcinoid Tumor

Esophageal carcinoma is a malignant tumor of the esophagus. The two major histological types are
esophageal adenocarcinoma and esophageal squamous cell carcinoma (SCC).

Also called

Small Bowel Neuroendocrine Tumor

ICD-10

C7A.019

Specialty

Gastroenterology

Onset

Chronic

Reviewed

July 2026

On This Page

Overview

  • Belongs to the group of neuroendocrine neoplasms (NENs).
  • May be functioning (secretes hormones causing symptoms) or nonfunctioning.
  • Small bowel neuroendocrine tumors account for a significant proportion of malignant small bowel tumors.
  • Carcinoid syndrome is mainly associated with metastatic gastrointestinal neuroendocrine tumors and can present with episodic flushing, diarrhea, abdominal pain, and wheezing.

Etiology & Risk Factors

-Etiology

  • Exact cause is unknown.
  • Most small bowel neuroendocrine tumors (carcinoid tumors) occur sporadically.

-Risk Factors

  • Positive family history of neuroendocrine neoplasms.
  • Genetic syndromes, especially:
  • Multiple endocrine neoplasia type 1 (MEN 1) (increases the risk of neuroendocrine neoplasms).

Pathophysiology

Neuroendocrine cells of the small bowel → Well-differentiated neuroendocrine tumor (carcinoid tumor) → Serotonin and other vasoactive substances produced → Liver metastasis → Hormones bypass liver metabolism → Enter systemic circulation → Carcinoid syndrome → Diarrhea (↑ intestinal motility and secretion) + Flushing (vasodilation) + Fibrosis (mesenteric fibrosis and carcinoid heart disease)

Clinical Presentation

    • Often asymptomatic in early stages.
    • Abdominal pain
    • Change in bowel habits or bowel obstruction (less common)
    • Carcinoid syndrome (usually with metastatic disease):
      • Episodic flushing
      • Secretory diarrhea
      • Wheezing/dyspnea
      • Diaphoresis
      • Hypotension
    • Advanced disease:
      • Carcinoid heart disease (right-sided valvular disease/right-sided heart failure)
      • Mesenteric fibrosis

History Taking

  • Ask about:

    • When did your abdominal pain start?
    • Where is the pain? Is it constant or intermittent?
    • Have you had diarrhea? How often?
    • Have you noticed episodes of facial flushing?
    • Do you have wheezing or shortness of breath?
    • Have you had unexplained weight loss?
    • Have you noticed nausea, vomiting, or signs of bowel obstruction?
    • Have you been told you have heart valve disease or symptoms of heart failure?
    • Is there a family history of neuroendocrine tumors or MEN 1?

Physical Examination

Assess for:

  • General: Weight loss, signs of malnutrition (advanced disease)
  • Vital signs: Hypotension (during flushing episodes)
  • Skin: Episodic flushing of the face, neck, and chest; diaphoresis
  • Abdomen: Abdominal tenderness or palpable abdominal mass (occasionally)
  • Respiratory: Wheezing
  • Cardiovascular (advanced disease):
  • Tricuspid regurgitation murmur
  • Signs of right-sided heart failure (e.g., peripheral edema, raised jugular venous pressure)

Investigations

  • Laboratory tests

    • 24-hour urinary 5-HIAA (for carcinoid syndrome)
    • Serum chromogranin A
    • Serotonin (when indicated)

    Imaging

    • Contrast-enhanced CT or MRI (localize tumor and assess metastases)
    • Somatostatin receptor PET/CT (preferred for staging and detecting small tumors/metastases)

    Histopathology

    • Biopsy to confirm diagnosis
    • Immunohistochemistry: Chromogranin A and Synaptophysin
    • Ki-67 index for tumor grading

Diagnosis

  • Diagnosis is confirmed by a combination of:

    • Clinical suspicion (e.g., flushing, diarrhea, abdominal pain)
    • Laboratory tests:
      • 24-hour urinary 5-HIAA (for carcinoid syndrome)
      • Serum chromogranin A
    • Imaging:
      • Contrast-enhanced CT or MRI
      • Somatostatin receptor PET/CT (preferred for staging)
    • Biopsy (gold standard):
      • Histopathology confirms the diagnosis
      • Immunohistochemistry: Chromogranin A and Synaptophysin
      • Ki-67 index for tumor grading
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Related Topics

Management

    • Multidisciplinary care (oncology, gastroenterology, surgery)
    • Observation for selected patients with small, indolent tumors and no carcinoid syndrome
    • Surgical resection for localized disease (treatment of choice)
    • Surgical debulking (cytoreduction) for selected metastatic disease to reduce symptoms and hormone production
    • Somatostatin analogues (e.g., octreotide) for carcinoid syndrome and to slow progression of metastatic tumors with somatostatin receptors
    • Radiolabeled somatostatin analogues for somatostatin receptor–positive tumors
    • Palliative chemotherapy for advanced disease
    • Liver-directed therapies (selected patients with liver metastases):
      • Hepatic arterial embolization
      • Radiofrequency ablation
      • Hepatic resection (when appropriate)

     

    Surgical resection is the main treatment for localized small bowel carcinoid tumors, while octreotide is the cornerstone of symptom control in carcinoid syndrome.

Complications

  • Carcinoid syndrome
  • Carcinoid heart disease (right-sided valvular heart disease)
  • Mesenteric fibrosis
  • Intestinal obstruction (ileus)
  • Intra-abdominal vessel ischemia
  • Ureteral obstruction
  • Metastatic spread (especially to the liver)
  • Carcinoid crisis (life-threatening; may be triggered by surgery, biopsy, or anesthesia)
  • The major complications are liver metastases, carcinoid syndrome, carcinoid heart disease, mesenteric fibrosis, and the potentially life-threatening carcinoid crisis.

Prognosis

  • Generally favorable if diagnosed early and completely resected.
  • Depends on:
  • Tumor stage
  • Presence of metastases
  • Tumor grade
  • 5-year survival: approximately 68% for malignant small bowel tumors overall.
  • If metastatic disease is present, 5-year survival decreases to approximately 40%.
  •  

Key Points / Clinical Pearls

  • A small bowel carcinoid tumor is a slow-growing, well-differentiated neuroendocrine tumor (NET) that arises from neuroendocrine cells of the small intestine.
  • Most tumors are sporadic and remain asymptomatic until advanced. Some produce serotonin, causing carcinoid syndrome (flushing, diarrhea, wheezing), which usually occurs after liver metastasis.
  • Diagnosis is based on 24-hour urinary 5-HIAA, serum chromogranin A, CT/MRI, somatostatin receptor PET/CT, and biopsy with Ki-67 grading.
  • Surgical resection is the treatment of choice for localized disease
  • while octreotide (somatostatin analogue) is the main treatment for carcinoid syndrome and unresectable metastatic disease.
  • Prognosis is generally favorable with early diagnosis but worsens in the presence of metastatic disease.
  • National Center for Biotechnology Information (NIH). Small Bowel Neoplasms, StatPearls.
  • Boudreaux JP, Klimstra DS, Hassan MM, et al; North American Neuroendocrine Tumor Society (NANETS). The NANETS Consensus Guideline for the Diagnosis and Management of Neuroendocrine Tumors: Well-Differentiated Neuroendocrine Tumors of the Jejunum, Ileum, Appendix, and Cecum. Pancreas. 2010;39:753-766. PMID: 20664473.
  • Howe JR, Cardona K, Fraker DL, et al. The Surgical Management of Small Bowel Neuroendocrine Tumors: Consensus Guidelines of the North American Neuroendocrine Tumor Society (NANETS). Pancreas. 2017;46:715-731. PMC5502737.
  • Diagnosis and Management of Small Bowel Neuroendocrine Tumors: A State-of-the-Art Review. PMC9516545.
  • MedlinePlus, National Library of Medicine (NIH). Carcinoid Syndrome: Medical Encyclopedia.