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Benign Tumors of the Small Intestine
Benign tumors of the small intestine are rare. In a series of 22,810 autopsies, the incidence was 0.16%. The neoplasms may be located anywhere in the small bowel. Stromal tumors, or leiomyomas, are more common in the jejunum, and adenomas are more common in the ileum. Both are benign but have significant malignant counterparts or potential. Benign tumors may be single or multiple. Adenomas, neurofibromas, and angiomas have a familial occurrence. Leiomyomas and adenomas are most common and, along with lipomas, myomas, some angiomas, and neurogenic tumors, make up more than two-thirds of lesions ( Fig. 72.1 ).
Benign Tumors of the Small Intestine.
Rarer benign tumors include fibromas, lymphangiomas, myxomas, and osteomas. Tumors may be intraluminal, extraluminal, or intramural. They may vary in size from millimeters to “very large” at 3 cm. Neurogenic tumors tend to appear in multiples, whereas adenomas, lipomas, and leiomyomas tend to appear singly. Neurogenic tumors in the small intestine may be part of a generalized neurofibromatosis (von Recklinghausen disease).
Benign vascular tumors of the small intestine comprise true tumors of blood vessels, or angiomas, and congenital vascular malformations, or hamartomas. These are difficult to differentiate and may be part of a generalized vascular dysplasia. Rendu-Osler-Weber syndrome (hereditary hemorrhagic telangiectasia), a mendelian-dominant disease, includes angiomas of the skin, mucous membranes, and viscera. Another mendelian-dominant inherited syndrome is Peutz-Jeghers syndrome, characterized by the association of gastrointestinal (GI) adenomas, polyposis, and a distinct type of mucocutaneous pigmentation ( Fig. 72.2 ). These polyps may be adenomatous or hamartomatous.
Top, Peutz-Jeghers Syndrome; Bottom, Complications of Benign Intestinal Tumors.
Brunner gland hamartomas and nodular lymphoid hyperplasia of the small intestine are benign tumors or polyps. Both are rare and frequently asymptomatic, but they require histologic definition.
Clinical Picture
In general, many of these benign lesions never cause symptoms, or cause such vague symptoms that a clinical diagnosis cannot be established. Serious clinical symptoms occur usually as a complication, such as intestinal obstruction, necrotic change in the tumor with resultant hemorrhage, infection, rupture, or malignant degeneration (see Fig. 72.2 ). Intraluminal tumors are likely to cause symptoms earlier than extraluminal tumors. Extraluminal lesions may grow to large dimensions before they become symptomatic. Intraluminal polypoid tumors may lead to obstruction by intussusception. This will manifest with an acute obstructive phenomenon or insidiously, with mild intermittent small bowel obstruction and symptoms of abdominal pain, vomiting, and either diarrhea or constipation. Severity of the symptom depends on the degree of obstruction and the site of the tumor.
Bleeding from the tumor is attributed to necrotic erosion of a vessel. It may be slow and insidious, or it may be massive and result in severe GI bleeding. Extraluminal tumors may rupture into the peritoneal cavity, or they may become necrotic after torsion of a pedicle and thus may lead to intraabdominal hemorrhage or an acute abdomen. In rare cases, fistulae may form through intramural or extraluminal tumors connecting the intestinal lumen with the abdominal cavity, resulting in peritonitis.
Malignant degeneration of benign tumors of the small bowel may occur. Adenomatous lesions are reported to develop into carcinoma in as many as 40% of patients. Similarly, leiomyomas (stromal tumors) are developing into leiomyosarcomas at an increasingly alarming rate.
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