Giant coeloadenoma of the kidney

A case of giant adenoma of the kidney is described with special regard to the histological and ultrastructural features of the neoplastic cells. The tumoral proliferation consisted mainly of clear and dark epithelial cells among which cells of a third type are occasionally interspersed. A possible origin of this last population from the coelomatic lining is suggested and the hypothesis of a dysontogenetic nature of the neoplasia is purposed.