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For further information, see CMDT Part 39-14: Malignancies of the Small Intestine

Key Features

Essentials of Diagnosis

  • Acute gastrointestinal (GI) bleeding with hematochezia or melena

  • Chronic GI blood loss resulting in fatigue and iron deficiency anemia

  • Obstruction resulting in vomiting

General Considerations

  • The frequency of different tumor types varies by location within the small intestine

    • Adenocarcinoma is most common in the duodenum and jejunum

    • Neuroendocrine tumors are most common in the ileum

    • Lymphomas and sarcomas each have similar incidences in the various segments of the small intestine

  • Adenocarcinomas are most often diagnosed at stage III or IV

  • Ampullary carcinoma incidence is increased > 200-fold in patients with familial adenomatous polyposis

  • Nonampullary adenocarcinoma of the small intestine: majority have metastasized at the time of diagnosis

  • Small intestinal adenocarcinomas are rare, with 11,790 new diagnoses estimated for 2022 in the United States

  • Patients with Crohn disease have an increased risk of small intestinal adenocarcinoma

  • Persons with Lynch syndrome have an increased risk of small bowel adenocarcinomas (4–8% of patients)

  • Lymphoma may arise primarily in the GI tract or involve it secondarily in patients with disseminated lymphoma

    • In the United States, primary GI lymphoma accounts for 5% of all lymphomas and 20% of small bowel malignancies

    • There is an increased incidence of small intestinal lymphomas in patients with AIDS, Crohn disease, and those receiving immunosuppressive therapy

    • Most common histologic subtypes are non-Hodgkin extranodal marginal zone (MALT) B cell lymphomas and diffuse large B cell lymphomas

    • Enteropathy-associated T cell lymphoma (EATL)

      • Appears to be increasing in incidence in the United States

      • Is associated with the diagnosis of celiac disease

    • In the Middle East, lymphoma occurs in immunoproliferative small intestinal disease

    • Other types of intestinal lymphomas include

      • Primary intestinal follicular cell lymphoma

      • Mantle cell lymphoma

      • Post-transplant lymphoproliferative disorder

      • Burkitt lymphoma

  • High-grade gastroenteropancreatic neuroendocrine neoplasms can be divided into

    • Well-differentiated neuroendocrine tumors Grade 3 (NETs G3) and

    • Poorly differentiated neuroendocrine carcinomas (NEC)

  • GI NETs (also called carcinoids) tumors account for one-third of small intestinal tumors

    • Most commonly occur in the small intestine (45%), primarily in the distal ileum within 60 cm of the ileocecal valve; jejunal-ileal NETs are the second most frequent location; up to 30% are multicentric

    • Secrete a variety of hormones, including serotonin, somatostatin, gastrin, and substance P

    • Most are malignant, though many behave in an indolent fashion

  • Sarcomas

    • Constitute ~ 10% of small bowel neoplasms and are commonly found in the jejunum and ileum (and in a Meckel diverticulum, if present)

    • Most arise from stromal tumors; a minority arise from smooth muscle tumors (leiomyosarcomas)

Clinical Findings

Symptoms and Signs

  • Most small bowel cancers have already metastasized at the time of diagnosis

  • Ampullary adenocarcinoma

    • Abdominal pain

    • Nausea

    • Jaundice due to bile duct obstruction

    • GI bleeding

  • Nonampullary adenocarcinoma of the small intestine

    • Symptoms of obstruction

    • Acute or chronic GI ...

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