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Cancer of the Small Intestine (Adenocarcinoma)

What kind of cancer affects the small intestine?

The small intestine, or small bowel, lies between the stomach and the colon. The small intestine is about 6 m (20 ft) long. Its primary function is to digest and absorb nutrients. The small intestine makes up more than 70% of the length and 90% of the surface area ofthe gastrointestinal (GI) tract.

The most common cancerous (malignant) tumors of the small bowel include adenocarcinoma, lymphoma, sarcoma, and carcinoids.

  • In industrialized countries, adenocarcinomas occur most often.
  • In developing countries, lymphomas are more common.
  • All these tumors have the potential to invade the bowel wall, spread into adjoining lymph nodes, and move to distant organs (metastasize).

What are the risk factors for cancer of the small intestine?

Malignant small intestine tumors occur in a small number relative to the frequency of tumors in other parts of the GI tract. There are many suggested reasons for this:

  • It has been proposed that the liquid nature of the small intestinal contents may be less irritating to the mucosa, the innermost lining of the small bowel.
  • Rapid transit time in the small bowel may reduce exposure of the intestinal wall to cancer-inducing agents found in the intestinal contents.
  • Other factors that might limit the presence or impact of potential cancer-inducing agents include the following:
    • A low bacterial count
    • A large lymphoid tissue component in the wall of the small intestine
    • An alkaline pH inside the small intestine
    • The presence of the enzyme benzpyrene hydroxylase
  • Adenocarcinoma of the small bowel is associated with the following underlying conditions:
    • Crohn's disease - An inflammatory disease of the small intestine. Crohn disease usually occurs in the lower part of the small intestine, called the ileum. The inflammation extends deep into the lining of the affected organ, causing pain and making the intestines empty frequently, resulting in diarrhea.
    • Celiac disease - Gluten intolerance
    • Familial polyposis syndromes - A group of inherited diseases in which small growths develop in the intestinal tract. In the case of familial adenomatous polyposis, while most polyps and later cancers appear in the large intestine, cancers arising in the small intestine do occur and are often found at the beginning of the small intestine in the duodenum.
  • Cancer is more common inthe large bowel than in the small bowel. Risk factors in the general population for small intestine cancer include the following:
  • Risk factors for developing cancer of the small intestine in Crohn's disease include the following:
    • Male sex
    • Long duration of disease
    • Associated fistulous disease: A fistula is an abnormal connection that passes from one surface to another, such as fromthe colon to the skin.
    • Surgical removal of part of the bowel
    • The risk of developing small intestinal cancer is 6 times greater for people with Crohn disease compared to the general population.
  • Lymphoma of the small intestine is associated with celiac disease but is also strongly associated with weakened immune systems such as occurs with AIDS.
Medically Reviewed by a Doctor on 6/3/2016
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