Renal oncocytoma. A review of the literature and report of an unusual multicentric case.

Renal oncocytoma is a rare tumour of the kidney composed exclusively of large polygonal cells with eosinophilic, granular cytoplasm. Ultrastructurally they are distinguished by the presence of large numbers of mitochondria and histochemically by abundant oxidative enzymes and adenosine triphosphate. Macroscopically these tumours are usually light brown in colour and commonly exhibit a dense central area of fibrous scarring, with fibrous trabeculae extending from this central zone in a stellate fashion. Renal oncocytomas are commoner in males than females (sex ratio 2:1) and although the age range at presentation is wide, there is a peak incidence in the seventh decade. The prognosis following surgical removal is excellent, despite the fact that many of these tumours are large. Invasion of the perirenal fat and the renal vein and metastatic spread to regional lymph nodes is documented, but death from metastatic disease is rare. The great majority of renal oncocytomas reported are solitary. We describe a multicentric renal oncocytoma, the sixth so far reported.