Small Bowel Neoplasms

Introduction

Neoplasms of the small intestine are rare, accounting for 3% to 6% of gastrointestinal neoplasms overall and 1% to 3% of primary gastrointestinal cancers. The incidence of small bowel cancer is higher in North American and Western European men compared with Asian men and women, and a higher incidence also has been noted in African American men and women. The prevalence of small bowel cancer, particularly carcinoid tumors, is increasing. The mean age at presentation is 65 years, with the incidence increasing after age 40 years.

More than 40 different histologic types of neoplasm may arise in the small intestine, and nearly 50% are malignant. Kopácová et al found that 42% of small intestinal neoplasms discovered in 170 patients by double balloon endoscopy were malignant; adenocarcinoma was the most common. Other malignancies include carcinoid, lymphoma, and gastrointestinal stromal tumor (GIST). Benign polyps include adenomas and hamartomas. Several hereditary syndromes have small intestinal polyps in their phenotypes (see Fig. 76-1 ).

The rarity of small bowel neoplasms is likely a result of several factors. The transit time through the small intestine is rapid, giving a brief mucosal contact time for potential carcinogens. Bacterial counts in the small intestine are lower than in the colon, so there is less processing of intestinal contents into carcinogens. A higher concentration of gastrointestinal lymphoid tissue and higher levels of immunoglobulin also are present. Finally, small intestinal contents are alkaline and liquid, which results in less chemical and mechanical stress on the mucosa and thus less inflammation.

Risk factors for small bowel cancer include Crohn disease and celiac disease. In both, the risk increases with the duration of the disease. In Crohn disease, the incidence of adenocarcinoma is higher among males with fistulizing disease of the distal jejunum or ileum. Celiac disease is associated with both lymphoma and adenocarcinoma. Lifestyle factors that have been reported in some studies to increase risk include red meat consumption, alcohol, smoking, and obesity. Gallstones appear to be associated with a higher risk for carcinoid tumors.

Presentation

The presentation of small intestine neoplasms varies. Symptoms include gastrointestinal bleeding and abdominal pain, whereas more advanced disease may present with bowel obstruction and weight loss. Some tumors are seen incidentally during an imaging study, and patients with lymphomas may present with fever, weight loss, and drenching night sweats. A small number of patients with liver metastases from carcinoid tumors present with the carcinoid syndrome, suggested by flushing, diarrhea, and bronchospasm.