The role of biopsy in the management of small renal tumors is increasing due to the characteristics of the contemporary patient population, new minimally invasive treatment modalities, and the improvements in biopsy technique and histopathological methods. This article reviews the recent developments on the percutaneous needle biopsy in small renal tumors. Small renal tumors have benign histopathology in about 20% to 40% of the cases, depending on the tumor size. Performing surgical resection without tissue diagnosis is “over treatment” for this group of patients. Since imaging can not accurately determine the characteristics of the tumors before the treatment yet, biopsy is the only method for histopathological evaluation. Needle biopsy is performed under imaging guidance via computerized tomography or ultrasonography percutaneously. At least two 18 G biopsy cores are obtained through a 17 G coaxial sheath. No needle tract seeding has been reported with this technique. In contemporary biopsy series accuracy for diagnosis is between 90% and 100%, and the false negativity rates are between 3% and 0%. Differentiation of malignant tumors with eosinophilic cytoplasm from oncocytoma and establishing accurate Fuhrman grading are two issues that cause difficulties in histopathologic evaluation of the renal biopsy. A re-biopsy after failed or indeterminate biopsy yields accuracy and malignancy rates similar to those obtained with the initial biopsy. Percutaneous needle biopsy is recommended before ablative therapies, active surveillance, and systemic treatment of patients without tissue diagnosis and it is stated that the biopsy should be performed via co-axial technique in the guidelines. It is reasonable to expect that pretreatment tissue diagnosis with needle biopsy is to become the routine clinical practice in the near future. (Bulletin of Urooncology 2014;13:161-164)

Keywords: Kidney neoplasms, carcinoma, renal cell; biopsy, needle