Metastatic renal oncocytic neoplasm with benign histologic appearance

We present a case of malignant renal oncocytoma which displayed a benign histologic appearance in the primary renal tumor and in metastases to the spine and liver. The case demonstrates the difficulty that may be encountered in distinguishing benign renal oncocytomas from malignant renal oncocytomas. Whereas, the accepted criteria will enable a distinction in the majority of instances, occasional instances may be encountered in which a benign histology does not provide an accurate reflection on the clinical course.