Renal oncocytoma with cylindromatous changes: pathologic features and histogenetic significance

We describe two cases of renal oncocytoma which showed an unusual light microscopic appearance characterized by nests of cells containing collections of eosinophilic hyaline material around and within oncocytic epithelial cell nests. Electron microscopy of the hyaline material showed a partly amorphous and partly lamellated structure, and immunohistochemistry for type IV collagen was positive. These cylindromatous changes are similar to the "glashelle Zylinder" of Billroth (Billroth T: Beobachtungen über geschwülste der speicheldrüsen. Virchous Arch [Pathol Anat] 17:357, 1859) described in adenoid cystic carcinoma and are most likely the result of an accumulation of basement membrane material in invaginations projecting into the surface of the basal plasmalemma. Since such invaginations occur in the normal distal tubule, our cases support origin of renal oncocytoma from distal tubular epithelial cells.