Argyrophil-negative G-cell duodenal carcinoid.

A case of mono-hormonal-producing and functionally active G-cell carcinoid tumor of the duodenum is described. The tumor, found to be argyrophil negative, was investigated immunohistochemically and ultrastructurally. We report our results, then discuss the possible histochemical causes that can lead to the failure of argyrophilia, and direct attention to the possible misdiagnosis that can result from that failure.