Coming from a urologist who spends half his clinical time treating small renal masses (SRMs), the vow never to treat SRMs may seem hard to believe and self-defeating.  However, times change, and I have reached the point where every time I hear about the treatment of the “small renal mass,” I bristle.

About five years ago in The Journal of Urology (2008;179:1227-1233), Robert G. Uzzo, MD, and colleagues published a review of treatment strategies for clinically localized renal masses in which they coined the phrase “the small renal mass dilemma.” The dilemma involved the seeming epidemic of SRMs being treated by urologists. The increased application of imaging technologies was identifying a large number of SRMs.

So, what is wrong with treating small incidentally discovered renal tumors? Clearly, early identification and treatment would save lives, right?  Sadly, the well-documented rising incidence and stable-to-rising mortality from renal tumors documents robust overtreatment.  Contemporary series report treatment of benign tumors in 25% or more of cases. Another 10%-15% of patients typically have indolent renal cell carcinoma (RCC) subtypes which may not require intervention in older patients with significant co-morbidities.  

The SRM dilemma really comes down to the identification of the incidental small renal tumors that require treatment. Aggressive histopathologic subtypes of RCC do require intervention, and can be identified with renal biopsy.


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However, unlike the vast majority of other tumors treated, there is great resistance to renal tumor biopsy. Three major concerns are typically cited:

  1. complications associated with the procedure
  2. the risk of tumor seeding
  3. lack of sensitivity and specificity of results

It is also likely that we urologists are guilty of historical inertia: Tumors discovered in the past were typically large and did not require biopsy as they had a high probability of being aggressive malignancies.

Historical concerns regarding SRM biopsy remain largely unfounded.  In recent series, the major complication rate is typically less than 1%, and only a handful of reports of tumor seeding exist in the literature. Recent series using needle core biopsies have also demonstrated high sensitivity and specificity. At the University of California Irvine, our team routinely performs renal tumor biopsy in the office setting under local anesthesia with success.

Routine biopsy of SRMs is safe and effective. Its application will avoid unnecessary surgery and its complications, and will save the healthcare system valuable resources. The time has come to end the SRM dilemma and vow to never treat SRMs again.