Primary adenocarcinoma of the small bowel is about 50 times less common than colonic carcinoma.
Almost 50% of small bowel adenocarcinomas are found in the duodenum, especially near the ampulla. In the remaining cases, the jejunum is more commonly involved than the ileum1.
Risk factors include a history of:
- Crohn disease;
- Peutz Jeghers syndrome;
- Lynch syndrome II;
- congenital bowel duplication;
- ileostomy or duodenal or jejunal bypass surgery.
More distal small bowel adenocarcinomas are more likely to be annular, duodenal adenocarcinomas tend to be papillary or polypoid1.
- CT shows a soft-tissue mass with heterogeneous attenuation, usually with moderate enhancement after intravenous administration of contrast material.
- may manifest as an annular narrowing with abrupt concentric or irregular “overhanging edges,” a discrete tumor mass or an ulcerative lesion.
- usually, only a short segment of the bowel is involved. Gradual narrowing of the lumen leads to partial or complete small bowel obstruction1.
A large, aggressive, ulcerated adenocarcinoma can be mistaken for lymphoma. However, lymph node metastases in adenocarcinoma are usually less bulky than those in lymphoma.
Small bowel malignant tumors:
Small bowel benign tumors:
- adenomatous polyp
- villous adenoma
- 1. Buckley JA, Fishman EK. CT evaluation of small bowel neoplasms: spectrum of disease. Radiographics. 1998;18 (2): 379-92. Pubmed citation