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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

  • Adenocarcinoma occurs most commonly in the duodenum

  • 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

  • Lymphoma may arise primarily in the GI tract or involve it secondarily in disseminated disease

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

    • Most common histologic subtype is non-Hodgkin extranodal marginal zone (MALT) B cell lymphoma

    • 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

  • Carcinoid tumors account for one-third of small intestinal tumors

    • Carcinoid tumors derive from neuroendocrine cells and may or may not secrete a number of hormones, including serotonin or its precursors

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

    • Even small carcinoid tumors may metastasize, usually by extension to the local lymph nodes and to the liver

    • Carcinoid syndrome occurs in < 10% of patients, usually in patients with hepatic metastasis; caused by tumor secretion of hormonal mediators

  • Most malignant sarcomas arise from stromal tumors that stain positive for CD117; Kaposi sarcoma is rare except in untreated AIDS

  • Most benign small bowel polyps occur singly; multiple polyps suggest a hereditary polyposis syndrome

  • Small bowel adenocarcinoma in young patients or those with a family history of gastrointestinal adenocarcinomas should prompt screening for Lynch syndrome (hereditary nonpolyposis colorectal cancer syndrome)

Clinical Findings

Symptoms and Signs

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

  • Adenocarcinomas

    • Abdominal pain

    • Nausea

  • Nonampullary adenocarcinoma of the small intestine

    • Obstruction

    • Acute or chronic bleeding

    • Weight loss

  • Ampullary carcinoma

    • Jaundice due to common bile duct obstruction

    • Bleeding

  • Primary lymphoma

    • Abdominal pain

    • Weight loss

    • Nausea and vomiting

    • Abdominal distention

    • Anemia

    • Occult blood in the stool

  • Carcinoid tumors

    • Most asymptomatic

    • Carcinoids are generally indolent tumors that spread slowly

    • May present with intermittent abdominal pain, bowel obstruction, or bowel infarction

    • Manifestations of carcinoid syndrome: facial flushing, edema of the head and neck (especially with bronchial carcinoid), abdominal cramps and diarrhea, bronchospasm, cardiac lesions (pulmonary or tricuspid stenosis or regurgitation), and telangiectases

  • Neuroendocrine tumors

    • Diarrhea

    • Flushing

    • Wheezing

Differential Diagnosis

  • Crohn disease

Benign polyps

  • Mucosal polyps: adenoma, hamartoma, hyperplastic

  • Lipoma

  • Benign stromal tumor (leiomyoma)

Malignant lesions

  • Adenocarcinoma

  • Lymphoma (primary or secondary)

  • Carcinoid


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