Observation of nervous tissue in a Wilms' tumor: its histogenetic significance.

A case of Wilms' tumor occurring in a horseshoe kidney is reported in which bona fide nervous tissue containing ganglion cells was observed. This finding cannot be reconciled with the currently held "metanephrogenic blastema" theory of the histogenesis of this tumor. Masson's concept of "neuroepithelial origin" of the Wilms' tumor should be re-evaluated.