- Small bowel tumors are relatively rare:
- Comprising only:
- 5% of all gastrointestinal malignancies
- Comprising only:
- Despite the small intestine being:
- 75% to 80% of the total length of the gastrointestinal tract:
- Small bowel adenocarcinomas are less common:
- Than colorectal adenocarcinomas
- This may be due:
- To the more dilute and liquid small bowel contents
- More rapid transit
- Decreased bacterial load (compared to the colon):
- Although the precise reasons for this low rate of malignancy are unknown
- This may be due:
- Than colorectal adenocarcinomas
- Small bowel adenocarcinomas are less common:
- 75% to 80% of the total length of the gastrointestinal tract:
- Estimated new cases and deaths from small intestine cancer in the United States in 2020:
- New cases:
- 11,110
- Deaths:
- 1,700
- New cases:
- Adenocarcinoma (36.9%), lymphoma (17.3%), sarcoma (8.4%), and carcinoid tumors (37.4%):
- Account for the majority of small intestine malignancies:
- Which, as a whole:
- Account for only 4% of all gastrointestinal malignancies
- Which, as a whole:
- Account for the majority of small intestine malignancies:
- Small bowel adenocarcinomas:
- Comprise approximately 37% of all small bowel malignancies:
- And are the second most common small bowel cancer:
- Slightly less common than small bowel carcinoid tumors (37.4%):
- 9.3 per million new cases of small bowel carcinoid tumor annually in the United States
- Slightly less common than small bowel carcinoid tumors (37.4%):
- And are the second most common small bowel cancer:
- Comprise approximately 37% of all small bowel malignancies:
- There are an estimated:
- 7.3 per million new cases of small bowel adenocarcinoma annually in the United States
- Small bowel adenocarcinomas:
- Arise in men slightly more often than in women:
- 53% versus 47%
- The median age at diagnosis:
- Is 67 years old
- Arise in men slightly more often than in women:

- Small bowel adenocarcinomas:
- Are thought to arise from adenomas:
- But the details of this process are less well understood:
- Than the natural history and biology of colorectal adenoma to adenocarcinoma development
- But the details of this process are less well understood:
- There are several known risk factors for small bowel adenocarcinoma, including:
- Familial syndromes:
- Lynch syndrome
- Familial adenomatous polyposis [FAP]
- Peutz-Jeghers syndrome
- Chronic inflammation:
- Crohn disease
- Celiac disease
- Previous colorectal adenocarcinoma.
- Familial syndromes:
- Are thought to arise from adenomas:
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