Since its original description in 1942 and its establishment as a distinct entity in 1976, the metastatic potential of renal oncocytoma has been the subject of considerable controversy. Throughout the years, several reports have claimed a low metastatic potential for these tumours, yet the debate remains. The 2004 World Health Organization¹ classification of renal tumours categorises renal oncocytomas as benign neoplasms. One of the reasons for this debate is that renal oncocytomas may be confused with clear cell renal carcinomas with a dominant eosinophilic component and—a more difficult differential diagnosis—with the eosinophilic variant of chromophobe renal cell carcinoma, a tumour with recognised low metastatic potential. The latter entity was first described by Thoenes et al² in 1985, although general recognition of this lesion had to wait for another 5 years. This may have delayed the awareness of potential confusion between chromophobe renal cell carcinoma and renal oncocytoma. In a large study of 166 oncocytomas published in 1991, the differential diagnosis of chromophobe carcinoma was not mentioned, although the authors recognised granular cell carcinoma as a potential source of misdiagnosis.³ …