Duodenal carcinoid tumor

(A) Low power view of a duodenal polyp biopsy specimen demonstrating replacement of the glandular compartment by an infiltrate of small blue cells.
(B) High power view of the same duodenal polyp reveals solid nests of uniform cells with basophilic cytoplasm. No mitosis identified. The features are characteristic of a duodenal neuroendocrine tumor (carcinoid tumor). Immunohistochemical stains may be helpful to categorize these tumors, which are positive on staining with antibodies to synaptophysin and chromogranin.