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Benign and malignant tumors (see Chapter 39-13 for Malignant Tumors) of the small intestine are rare, accounting for 3–6% of gastrointestinal neoplasms. They often cause no symptoms or signs. However, they may cause acute gastrointestinal bleeding with hematochezia or melena or chronic gastrointestinal blood loss resulting in fatigue and iron deficiency anemia. Small bowel tumors may cause obstruction due to luminal narrowing or intussusception of a polypoid mass. Neuroendocrine tumors may present with diarrhea, flushing, or wheezing. Small bowel tumors usually are identified by video capsule endoscopy, CT or MR enterography, or barium small bowel series. Visualization and biopsy of duodenal and proximal jejunal mass lesions are performed with a long upper endoscope known as an enteroscope.

Benign polyps may be symptomatic or may be incidental findings detected on endoscopy or radiographic study. Most occur singly, and the presence of multiple polyps is suggestive of hereditary polyposis syndrome (discussed under Diseases of the Colon and Rectum). With the exception of lipomas, surgical or endoscopic excision usually is recommended.

Adenomatous polyps are the most common benign mucosal tumor. The majority are asymptomatic, though acute or chronic bleeding may occur. Because malignant transformation does occur, endoscopic or surgical resection is warranted. Villous adenomas occur most commonly in the periampullary region of the duodenum (especially in patients with familial adenomatous polyposis) and carry a high risk for development of invasive cancer. Periodic endoscopic surveillance to detect early ampullary neoplasms is recommended in patients with familial adenomatous polyposis. Evaluation with endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasound is required to exclude invasive carcinoma. Ampullary adenomas may be removed by endoscopic or surgical techniques. Lipomas occur commonly in the ileum. Most are asymptomatic and identified incidentally at endoscopy or radiography; however, they rarely may cause obstruction with intussusception (eFigure 15–63).

eFigure 15–63.

Duodenal intussusception. CT scan of the abdomen at the level of the distal portion of the descending duodenum. The duodenum is markedly enlarged and has the appearance of a circle within a circle (arrows). This is the typical appearance of an intussusception, with the intussuscepting segment in the center and the receiving segment (intussusceptum) on the periphery.

Benign mesenchymal tumors are found at all levels of the intestine. These submucosal mesenchymal lesions may be intraluminal, intramural, or extraluminal. Although most are asymptomatic, they may ulcerate and cause acute or chronic bleeding or obstruction. It is difficult to distinguish benign from malignant stromal tumors except by excision. The management of gastrointestinal mesenchymal tumors is discussed in Chapter 39-13.

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de Latour  RA  et al. Management of small bowel polyps: a literature review. Best Pract Res Clin Gastroenterol. 2017 Aug;31(4):401–8.
[PubMed: 28842049]  

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