Polypoid nonchromaffin paraganglioma of the duodenum.

A polypoid tumor was surgically removed from the second part of the duodenum of a 56-year-old male. The main body consisted of large epithelioid cells arranged in an adenoma like pattern of strands and nests. These cells were argyrophil and had marked nonspecific esterase activity. Unmyelinated nerves with proliferated Schwann cells accompanied these epithelioid cells together with scattered gangliocyte like elements. Ultramicroscopically, the epithelioid cells were seen to contain round electron dense granules, 150 nm in diameter on average. The tumor is considered to be a nonchromaffin paraganglioma, as it probable developed from paraganglion cells associated with small arteries or branches of the vagus nerve, or from the undifferentiated pluripotent APUD cells of the duodenum.