Renal oncocytoma. II. Lectin and immunohistochemical features indicating an origin from the collecting duct.

The present study is aimed to gain more insight into the histochemical properties of renal oncocytomas. Ten oncocytomas and normal kidneys were investigated using several lectins (peanut agglutinin--PNA, Dolichos biflorus agglutinin--DBA and Ulex europaeus agglutinin--UEA) and antibodies against epithelial membrane antigen (EMA), Tamm-Horsfall glycoprotein (THG) and lysozyme. Lectin histochemistry revealed a characteristic binding pattern in renal oncocytomas, with strong DBA-binding and, in some cases, a weaker staining with UEA apparent in the cytoplasm of the oncocytes. PNA binding sites were evident only after enzymatic cleavage of sialic acid by neuraminidase. Comparative evaluation of normal kidneys exhibiting a strict compartmentalization of saccharide moieties in the various nephron segments revealed a similar binding pattern exclusively in interspersed collecting duct epithelium. This striking resemblance suggests that renal oncocytomas may originate from the collecting duct system. Further support for this assumption has been provided by the demonstration of strong cytoplasmic EMA reactivity in the oncocytes. In normal kidneys prominent labeling for EMA was apparent in the very same interspersed cells of the collecting ducts. THG and lysozyme failed to react in renal oncocytomas. In accordance with observations recently reported in the literature, these results clearly favor a histogenetic origin of renal oncocytomas from the collecting duct epithelium.