Oncocytic variant of papillary renal cell carcinoma – should it be classified as a distinct subtype?

Renal tumor classification has evolved during the last several decades based on different microscopic and molecular patterns. We present a case of a renal mass which on evaluation revealed a radiologically, histologically and immunologically distinct pattern from the currently described subtypes. Evaluation of the histology of our patient revealed it to have features of papillary renal cell carcinoma with atypical features not conforming to either category of the two currently described subtypes. This atypical pattern consisted of oncocytic cells with malignant features organized in papillary architecture. Analogous oncocytic tumors have been described in tumours in other organs including thyroid and parotid gland. This oncocytic variant is distinct from the two subtypes of papillary renal cell carcinoma as well as the commonly described benign oncocytoma both microscopically and radiologically. Establishing this as a separate subtype may help in better treatment and prognostication.