Oncocytic papillary renal cell carcinoma: potential pitfall in small enucleation

OBJECTIVE: We describe an emerging entity, recently recognized as a pitfall in the diagnostic practice among eosinophilic renal cell tumours. METHODS: A 60-year-old male underwent enucleation of a 1.2 cm nodule. Immunohistochemistry and FISH analysis were performed. RESULTS: Histology revealed a neoplasm composed of large cells with eosinophilic cytoplasm, Fuhrman grade 3, arranged in papillae. At the immunohistochemical level, cells showed positivity for AMACR and CD10. Fluorescence in situ hybridization (FISH) demonstrated gains of chromosomes 7 and 17 and loss of Y. A diagnosis of oncocytic papillary renal cell carcinoma was made. CONCLUSIONS: The distinction between renal oncocytoma and oncocytic papillary renal cell carcinoma is of substantial importance because of their different behaviour and prognosis, since the latter has malignant potential. Although the available evidence supporting tumour enucleation as the surgical treatment for renal cortical tumours < or = 4 cm, due to aforementioned clinicopathological features such tumours need to be evaluated using appropriate immunophenotypical and cytogenetic analyses.