Small Intestinal Neoplasms

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 ...