A case of oncocytic papillary renal cell carcinoma.

Papillary renal cell carcinomas (RCC) are the second most frequently identified pathological subtypes of RCC. Occasionally, papillary RCC demonstrate pathological characteristics of renal oncocytomas (RO), benign renal tumors. We report the case of an 81-year-old woman with an oncocytic papillary RCC, which was difficult to differentiate from a hybrid of RO and papillary RCC, who underwent left radical nephrectomy. Morphological examination showed oncocytic tumor region and partially scattered regions with papillary structure. Immunohistochemical examinations demonstrated strongly positive staining of alpha-methylacyl-CoA racemase in the papillary region and negative staining of progesterone receptor and CD117 in both regions. Fluorescence in situ hybridization confirmed the increased number of copies of chromosome 7 in the papillary region. Comprehensively, this case could be diagnosed as oncocytic papillary RCC. No evidence of disease recurrence was found at 12 months' follow up.