Renal oncocytoma. Pathological evaluation and clinical implications.

Renal oncocytoma is a benign tumour of renal tubular origin; oncocytes are transformed epithelial cells rich in mitochondria, probably representing senescent degenerative cellular changes. Most of renal oncocytomas usually follow a benign clinical course and partial nephrectomy or enucleation has been advocated as curative. By immunohistological staining of tissue sections using monoclonal antibodies (DBA, SBA, PNA, UEA, Cytocheratine), we can suppose the histogenetic origin of renal oncocytomas from a region other than the proximal tubular epithelium, and in particular from the collecting duct epithelium. We believe that it is most important to perform flow cytometry to study the chromosomal pattern of the tumour, once intra-operative frozen sections have advanced the suspicion of renal oncocytoma; if oncocytic cells show a diploid pattern, and the tumour mass is well circumscribed and has not an excessive diameter, we favour renal sparing surgery.