Core needle biopsy clarify the histology of the small renal masses and may prevent overtreatment.

PURPOSE: The purpose of the study was to evaluate the diagnostic accuracy of core biopsy in small renal masses ≤ 4 cm in response to the rising prevalence of renal masses.

METHODS: Data from 129 consecutive patients who underwent biopsies of solid renal masses of ≤ 4 cm were prospectively collected between September 2014 and January 2017. In cases with inconclusive biopsies, a repeat biopsy was recommended. Histology from surgical specimens was used as gold standard to evaluate the accuracy of renal biopsies.

RESULTS: The initial biopsies revealed malignancy in 77 patients (59.7%) and benign histology in 35 patients (27.1%), whereas 17 (13.2%) were inconclusive. Fifty-six patients with malignant histology underwent either partial or radical nephrectomy according to the physicians' recommendation, while two patients with benign histology requested surgery. In all cases, the biopsy diagnosis was confirmed upon final histopathology. Of the inconclusive cases, six underwent repeat biopsies all with benign histology. Further, three patients opted for immediate partial nephrectomy with benign oncocytoma in two and renal cell carcinoma in the third. The remaining eight patients opted for follow-up CT scans with no sign of progression with a minimum of 6-month follow-up. No biopsy related complications were reported in the first 30 days after RTB. Overall, the treatment strategy changed in 45 of 129 (35%) patients due to biopsy results. This was either due to benign findings or due to the discovery of non-renal cell cancers.

CONCLUSION: Core needle biopsies of solid renal masses ≤ 4 cm have excellent accuracy and may be used to select the correct treatment. Importantly, they may serve to prevent overtreatment of benign tumors.