There has been a considerable increase in the detection of small renal masses (SRM). Approximately 20% of these turn out to be benign lesions on final histopathological analysis. Therefore upfront surgery can be overtreatment in such a group of patients. Active surveillance has been proposed as an option to manage SRMs, though most urologists remain wary of the risks of adopting this approach especially in younger patient groups.
Renal mass biopsy (RMB) can be used as an adjunct to AS, but despite improved diagnostic outcomes, RMB has not been widely utilised. In this multicentre study of four high-volume Canadian centres, authors evaluated whether the centres who routinely performed RMB (group A), have a lower incidence of benign pathology on final surgical specimen compared to those who only selectively perform RMB (group B). Five hundred and sixteen patients with 542 SRMs (less than 4cm) were included who had either partial or radical nephrectomy performed. A total of 192 (35%) SRMs were biopsied preoperatively. The biopsy rate was significantly higher in group A (63%) versus group B (12%). Biopsies were considered diagnostic in 95% of cases. Overall 11% of patients had benign histology on final surgical specimen. In group A, only 5% of cases had benign pathology compared to 16% in group B. In Group A, 11 of the 12 benign cases had not been biopsied preoperatively.
The authors also found concordance between RMB and surgical histology in 84% of cases (161 of 192 cases) in diagnosing histopathological tumour type. In the 110 cases of clear cell RCC on RMB and surgical histology, there was concordance on Fuhrman grading in 55% (61 cases). In all discordant cases, RMB underestimated the true grading compared to surgical pathology. Another important finding was that each 1cm increase in size was associated with a 30% decrease in the odds of finding a benign final surgical pathology. This study suggests that more routine use of RMB in appropriately selected cases can reduce overtreatment of SRM and hence reduce treatment related morbidity.