Adenoma and Adenocarcinoma of the Small Intestine
Definition
- Benign and malignant epithelial neoplasms arising in the ampulla of Vater, duodenum, jejunum or ileum
Covered separately:
- Endocrine neoplasms of the duodenum (including proximal jejunum) and ileum
- Small cell (undifferentiated) carcinoma of the GI tract
Diagnostic Criteria
- Adenomas and adenocarcinomas of the small intestine are rare
- Approximately half occur in the duodenum
- Many of these are ampullary
- Metastases are more common than primary carcinomas
- Many adenomas and carcinomas are associated with defined syndromes and diseases (see full descriptions)
- Familial adenomatous polyposis
- Duodenum
- 97% lifetime risk of adenoma
- 3-4% lifetime risk of carcinoma
- Terminal ileum at time of colectomy:
- 2% have a grossly visible adenoma
- 4-5% have an adenoma on random sections
- Ileal pouch
- >50% will develop adenomas
- May be up to 50 polyps
- Carcinoma may infrequently develop
- Hereditary non-polyposis colorectal carcinoma syndrome
- Low but clearly elevated risk of small intestine carcinoma
- Juvenile polyposis syndrome
- Rare duodenal carcinoma
- Peutz-Jeghers syndrome
- 13% lifetime risk of small intestine carcinoma
- Misplaced glands in stalk should not be mistaken for carcinoma
- Crohn disease
- Carcinomas mostly occur in the ileum
- Risk increases significantly after about 10 years
- Celiac disease
- Low but clearly elevated risk of small intestine carcinoma
- Same histologic features as colorectal adenomas and adenocarcinomas
- Rare mixed types have been reported
- Adenosquamous
- Tripartite (endocrine, squamous and adenocarcinoma)
- Also rarely reported in the duodenum
- Hyperplastic polyp
- Serrated adenoma
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates : 11/29/09, 8/21/10, 2/12/11
