Аннотация:The differential diagnosis between renal oncocytoma (RO) and chromophobe renal cell carcinoma (chRCC) is clinically significant because of their different biological behavior: the former widely accepted as a benign neoplasm and the latter largely considered as malignant tumor with potential for metastatic spread. The light microscopy differentiation of RO and chRCC may be problematic due to the overlapping morphology among these neoplasms and further investigations are needed to define the correct diagnosis. The aim of this study was to investigate the ultrastructural peculiarities of RO and chRCC and to examine the value of electron microscopy in differentiating between these neoplasms.