Fine needle aspiration biopsy cytology of renal oncocytoma

The cytologic appearance of cells in fine needle aspiration biopsies of two cases of well-differentiated renal oncocytoma (grade 1) and one case of moderately well differentiated renal oncocytoma (grade 2) is presented. In grade 1 renal oncocytoma, the tumor cells were seen mainly singly or in small clusters; they were round or polygonal, with abundant granular and eosinophilic cytoplasm and small, regular, round, hyperchromatic nuclei. Aspirated cells from the grade 2 renal oncocytoma were seen mainly in large sheets. These cells were polygonal, with eosinophilic, granular cytoplasm and slightly irregular vesicular nuclei with prominent nucleoli.