Nonchromaffin paraganglioma of the duodenum.

A benign nonchromaffin paraganglioma of the duodenum is described and compared with other reported cases. Duodenal location is extremely rare but the morphology, based on the optical microscopic pattern (Zellballen) and the ultrastructural appearance is, comparable with paragangliomas of other sites. The lack of nerve fibres and ganglion cells in this tumour, together with the absence of a positive chromaffin reaction permits us to classify it as a pure nonchromaffin paraganglioma. This finding constitutes indirect evidence of the probable existence of a paraganglion in the duodenal wall, a structure not yet demonstrated in the adult.