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Small bowel carcinoid tumor

Small bowel carcinoid tumors are the most common gastrointestinal carcinoid tumors and most frequently involves the terminal ileum.

Small bowel carcinoid tumors account for ~40% of gastrointestinal carcinoid tumors 1

Small bowel carcinoids are slow growing and may present with vague symptoms 1,3:

  • weight loss
  • fatigue
  • diarrhea
  • abdominal pain

More specific symptoms include:

Carcinoid tumors are neuroendocrine tumors arising from APUD cells. They can cause a desmoplastic reaction in nearby tissue, leading to fibrosis and tethering of the adjacent bowel 1,3 (for further discussion, see the main article).

The primary tumor in small bowel carcinoid is typically only up to 3.5 cm in size. Metastases, commonly to the mesentery, liver, and lymph nodes, often exceed the size of the primary neoplasm. Multiple primaries and metachronous tumors in other organs can often occur 3.

About 45% (range 30-60%) of patients with small bowel carcinoid have metastatic disease at presentation 1,3. The larger the primary, the greater the likelihood of metastases 4.

On CT, the primary lesion is often polypoid or plaque-like, and hyperenhancing 3. However, due to their small size, the primary is not always seen on imaging 4. They can cause distortion of the small bowel and fixed, “hairpin” kinks in the course of the small bowel 1. The primary contains calcification in up to 70% of cases 4.

Mesenteric metastases can appear well-defined or spiculated on CT, with stranding due to fibrosis and desmoplastic reaction (leading to a characteristic “spoke-like” appearance of mesenteric vessels) 1,3.

In the liver, metastases strongly enhance in the arterial phase due to their vascularity 4, then become isodense to liver parenchyma in the delayed phase.

Carcinoid syndrome mainly treated by somatostatin analog therapy. Everolimus is use as 2nd line of treatment 5

Article information

rID: 56226
Synonyms or Alternate Spellings:
  • Small bowel carcinoid tumours
  • Small bowel carcinoid
  • Small bowel carcinoids
  • Small bowel carcinoid tumors
  • Small bowel carcinoid tumor

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Cases and figures

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  • Case 10: mesenteric metastases
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