CT evaluation of small bowel neoplasms: spectrum of disease.

Neoplasms of the small bowel are rare lesions that account for less than 5% of all gastrointestinal tumors. Although the differential diagnosis for a small bowel tumor is extensive, various small bowel neoplasms have characteristic features at computed tomography (CT) that may aid in making a diagnosis. Small bowel adenocarcinoma may appear at CT as an annular lesion, a discrete nodular mass, or an ulcerative lesion. Non-Hodgkin lymphoma may appear as a segmental bulky mass that gradually merges into the normal bowel wall. Lymphoma is characteristically associated with marked luminal dilatation. Carcinoid tumor may appear as an ill-defined homogeneous mass that displaces bowel loops. Calcification and desmoplastic reaction in a mesenteric mass suggest the diagnosis of carcinoid tumor. Gastrointestinal stromal tumors (GISTs), both benign and malignant, may be submucosal, subserosal, or intraluminal. The CT appearance of a GIST may include a sharply defined mass with homogeneous attenuation, sometimes with calcification. Lipoma appears at CT as a well-circumscribed, intraluminal homogeneous mass with fat attenuation. Most malignant small bowel tumors are actually metastases that have spread intraperitoneally, hematogenously, or by local extension. Intraperitoneal seeding usually manifests at CT as multiple small nodular metastases along the small bowel serosa, mesentery, and omentum. In patients with Peutz-Jeghers syndrome, nonneoplastic lesions may mimic small bowel neoplasms.