A case of liver metastasis from an oncocytoma with a focal area of chromophobe renal cell carcinoma: a wolf in sheep's clothing.

In 2004, the World Health Organization classified the renal oncocytomas as benign neoplasms of the kidney. There are reports of subtypes of renal tumors, with similar histological morphology to oncocytoma, but with malignant potential, one of these tumors is the eosinophilic variant of chromophobe renal cell carcinoma. It is important to characterize the histological features and the subtype of tumor, as this predicts biological behavior and cancer-specific survival rate. A rare case of a liver metastasis from a focal area of eosinophilic variant of chromophobe renal cell carcinoma mixed in oncocytoma in a 69-year-old woman is reported. Although some renal tumors may contain oncocytoma and eosinophilic variant of chromophobe renal cell carcinoma histology, caution should be exercised while diagnosing oncocytomas in needle biopsies as there may be unsampled area of chromophobe carcinoma which has a potential for metastatic spread representing a wolf in sheep's clothing.