Chapter 087. Gastrointestinal Tract Cancer (Part 14)

Tumors of the Small Intestine Small-bowel tumors comprise
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Chapter 087. Gastrointestinal Tract Cancer (Part 14) Chapter 087. Gastrointestinal Tract Cancer (Part 14) Tumors of the Small Intestine Small-bowel tumors comprise small-bowel barium study is the diagnostic procedure of choice; the diagnosticaccuracy may be improved by infusing barium through a nasogastric tube placedinto the duodenum (enteroclysis). Benign Tumors The histology of benign small-bowel tumors is difficult to predict onclinical and radiologic grounds alone. The symptomatology of benign tumors isnot distinctive, with pain, obstruction, and hemorrhage being the most frequentsymptoms. These tumors are usually discovered during the fifth and sixth decadesof life, more often in the distal rather than the proximal small intestine. The mostcommon benign tumors are adenomas, leiomyomas, lipomas, and angiomas. Adenomas These tumors include those of the islet cells and Brunners glands as well aspolypoid adenomas. Islet cell adenomas are occasionally located outside thepancreas; the associated syndromes are discussed in Chap. 344. Brunners glandadenomas are not truly neoplastic but represent a hypertrophy or hyperplasia ofsubmucosal duodenal glands. These appear as small nodules in the duodenalmucosa that secrete a highly viscous alkaline mucus. Most often, this is anincidental radiographic finding not associated with any specific clinical disorder. Polypoid Adenomas About 25% of benign small-bowel tumors are polypoid adenomas (Table87-5). They may present as single polypoid lesions or, less commonly, as papillaryvillous adenomas. As in the colon, the sessile or papillary form of the tumor issometimes associated with a coexisting carcinoma. Occasionally, patients withGardners syndrome develop premalignant adenomas in the small bowel; suchlesions are generally in the duodenum. Multiple polypoid tumors may occurthroughout the small bowel (and occasionally the stomach and colorectum) in thePeutz-Jeghers syndrome. The polyps are usually hamartomas (juvenile polyps)having a low potential for malignant degeneration. Mucocutaneous melanindeposits as well as tumors of the ovary, breast, pancreas, and endometrium arealso associated with this autosomal dominant condition. Leiomyomas These neoplasms arise from smooth-muscle components of the intestineand are usually intramural, affecting the overlying mucosa. Ulceration of themucosa may cause gastrointestinal hemorrhage of varying severity. Cramping orintermittent abdominal pain is frequently encountered. Lipomas These tumors occur with greatest frequency in the distal ileum and at theileocecal valve. They have a characteristic radiolucent appearance, are usuallyintramural and asymptomatic, but on occasion cause bleeding. Angiomas While not true neoplasms, these lesions are important because theyfrequently cause intestinal bleeding. They may take the form of telangiectasia orhemangiomas. Multiple intestinal telangiectasias occur in a nonhereditary formconfined to the gastrointestinal tract or as part of the hereditary Osler-Rendu-Weber syndrome. Vascular tumors may also take the form of isolatedhemangiomas, most commonly in the jejunum. Angiography, especially duringbleeding, is the best procedure for evaluating these lesions. Malignant Tumors While rare, small-bowel malignancies occur in patients with long-standingregional enteritis and celiac sprue as well as in individuals with AIDS. Malignanttumors of the small bowel are frequently associated with fever, weight loss,anorexia, bleeding, and a palpable abdominal mass. After ampullary carcinomas(many of which arise from biliary or pancreatic ducts), the most frequentlyoccurring small-bowel malignancies are adenocarcinomas, lymphomas, carcinoidtumors, and leiomyosarcomas. Adenocarcinomas The most common primary cancers of the small bowel areadenocarcinomas, accounting for ~50% of malignant tumors. These cancers occurmost often in the distal duodenum and proximal jejunum, where they tend toulcerate and cause hemorrhage or obstruction. Radiologically, they may beconfused with chronic duodenal ulcer disease or with Crohns disease if the patienthas long-standing regional enteritis. The diagnosis is best made by endoscopy andbiopsy under direct vision. Surgical resection is the treatment of choice.