Small renal masses: current concepts regarding the natural history and reflections on the American Urological Association guidelines

Purpose of review Although surgical resection is the current standard for treatment of small (<4 cm) renal cortical neoplasms, active surveillance remains an option in selected patients depending on tumor characteristics and surgical risk. We review the natural history of small renal masses according to the current literature, and highlight issues regarding the recent guidelines for the management of T1 renal masses put forth by the American Urological Association. Recent findings The natural history of small renal masses is still largely unknown; however, initial size or volume of the mass seems to predict the risk of malignancy in retrospective studies. A new study found that growth rate is inversely related to initial tumor volume, with smaller masses growing faster in the beginning and decreasing in rate of growth as they enlarge. Biomarkers such as carbonic anhydrase IX, vascular endothelial growth factor, and CD147 have demonstrated some value in predicting tumor characteristics and prognosis in renal cell carcinoma. Finally, we suggest modifications to the new American Urological Association guidelines based on the authors' experience in order to optimize the management of renal cortical neoplasms. Summary The natural history of small renal masses is not completely understood. Growth rate and tumor size are factors shown to be predictive of tumor biology. Currently, there are no specific tumor markers to determine initial risk or progression to metastatic disease; however, investigation into new molecules is being undertaken. The guidelines presented by the American Urological Association give a formal framework for the management of T1 renal cortical neoplasms; however, we site specific modifications and recommend that they be considered when evaluating patients for treatment.