Adenomatoid tumor of the small intestine: the first case report and review of the literature.

The case represents the first literature report of an adenomatoid tumor that arises primarily in the small intestine of a 44-year-old woman, who presented with intermittent upper abdominal pain accompanied by nausea and vomiting. The resected tumor was grossly unencapsulated and had a gray-tan color on its cut surface. Microscopically, it consisted of variably sized tubules and glandular spaces which involved the whole layers of the intestine. The mesothelial nature of the lesion was subsequently verified by the immunopositivity for pancytokeratin (AE1/AE3), HBME-1, calretinin, D2-40, and WT1 with cells lining the tubules and glandular spaces. Albeit very rare, adenomatoid tumor should be included in the differential diagnosis of tubular or glandular tumors occurring in the small intestine.