Renal oncocytoma-are there sufficient grounds to consider surveillance following prenephrectomy histologic diagnosis

Introduction: Oncocytoma is a benign neoplasm of the kidney and comprises about 12% of all renal masses. A definitive preoperative diagnosis of oncocytoma is currently technically not feasible and its practical implication is controversial. Objectives: To analyze the current status of preoperative diagnostic tools for oncocytoma, study the different occurrences of oncocytoma-renal cell carcinoma (RCC) coexistence, including the phenomenon of true hybrid tumors, and investigate the rare reports on the natural history of unresected oncocytoma. Materials and methods: A PubMed search was performed using the following key word: oncocytoma, renal cell carcinoma, natural history, electron microscopy, and cytogenetics. Medline articles and abstracts prior to August 2009 were reviewed. Results and conclusions: At the moment, preoperative renal mass biopsy is the only way for prenephrectomy histologic diagnosis of oncocytoma. However, it is expected that some of these biopsies, although suggestive for oncocytoma, will suspect chromophobe RCC. In all the English literature, the number of true ipsilateral synchronous hybrid oncocytoma-RCC tumors is extremely low in comparison with the "pure" oncocytomas being resected worldwide. There is almost no data on the natural history of oncocytoma.