Long-Term Follow-Up in Patients Undergoing Renal Mass Biopsy: Seeding is not Anecdotal

INTRODUCTION

Renal biopsy is recommended if the outcome might alter therapeutic decisions for patients who present with renal masses of unclear etiology. However, little is known about long-term risks related to this procedure.

PATIENTS AND METHODS

We performed a retrospective analysis of an institutional database maintained by a tertiary referral center that included patients who underwent renal biopsies between 2003 and 2005 with a follow-up of at least 15 years. Renal biopsies were taken percutaneously with a coaxial technique according to guideline recommendations and included off-line ultrasound guidance.

RESULTS

We identified 106 patients who underwent biopsies for a renal mass of unclear etiology. The median age was 58.7 years (43.7-66.2). A median of 4.2 (3-6) biopsies were collected from each patient. Tumor seeding leading to local growth was identified in 6 patients (5,7%) after a median follow-up of 8.2 years. Four of these lesions that were resected exhibited the same histology as the original biopsy result; these patients experienced no further recurrence. In 45 patients (42%), the biopsy results led to a therapy other than surgery (n = 28 lymphoma, n = 6 metastasis from other malignancies, n = 11 oncocytoma). The remaining 61 patients (58%) were diagnosed with renal cell carcinoma treated either surgically or with ablation. None of the patients developed metastatic spread related to tumor seeding.

CONCLUSION

Tumor seeding after renal mass biopsy is a rare, but relevant risk associated with this procedure. As indications for renal mass biopsy increase, longer-term follow-up and improved biopsy techniques should be considered to address this complication.

Renal Mass Biopsy

Kidney cancer accounts for 2% of cancer related deaths. Historically, a patient with a solid renal mass would undergo surgery without biopsy given the previously low diagnostic yield of biopsy and the fear of tumor seeding. This led to a high rate of resection for benign masses. With the rising incidence of renal masses discovered on imaging, improvements in biopsy technique and advancements in pathologic evaluation of biopsy samples of renal masses, renal mass biopsy now plays an important role in selected patients with renal masses. Coaxial core needle biopsy is the preferred technique with a low rate of complications and a high diagnostic yield. This article will discuss indications, methods, utility, limitations and complications of renal mass biopsy.

To stage or not to stage: determining the true clinical significance of the biopsy tract through perinephric fat in assessing renal cell carcinoma

AIMS

Perinephric fat invasion (PFI) is a key component of renal cell carcinoma (RCC) staging, but there are limited data pertaining to biopsy tract seeding (BTS) resulting in perirenal tissue involvement [BTS with perinephric fat invasion (BTS-P)].The aim is to correlate clinical outcomes with pathologic stage to determine whether the presence of BTS-P should be considered a criterion to stage RCC as part of the pT3a category in the absence of any other upstaging variables.

MATERIALS AND RESULTS

We identified 304 renal biopsies from patients with subsequent nephrectomies for RCC; 33 of the tumours contained PFI. Each case was reviewed to determine the presence of BTS-P and other forms of invasion [e.g. non-BTS-P PFI, sinus fat invasion (SFI), and/or renal vein invasion (RVI)], and these findings were compared with survival outcomes. Ten (30%) of 33 tumours with PFI showed BTS-P as the only finding, and were otherwise pT1 tumours; six (60%) patients were alive without disease (AWOD) (mean, 77.5 months), three were lost to follow-up (LTF), and one died of other disease (DOOD). Two patients showed true PFI plus BTS-P; one was LTF and one is AWOD at 107 months. Ten (43%) of 23 patients with tumours with true invasion (PFI ± SFI and/or RVI) are AWOD (mean, 97.7 months), eight (35%) died of disease (DOD), four were LTF, and one DOOD. Kaplan-Meier survival curves showed that the cancer-specific survival was significantly worse in patients with true invasion (P = 0.044) than in those with BTS-P as the sole finding.

CONCLUSION

Patients with tumours showing BTS-P only appear to have better outcomes than those with other non-PFI invasion, suggesting that this finding should not be upstaged to pT3a. Additional studies are needed to corroborate the significance of our observations.

Needle Biopsy Adequacy in the Era of Precision Medicine and Value-Based Health Care

CONTEXT.—

Needle biopsy of diseased tissue is an essential diagnostic tool that is becoming even more important as precision medicine develops. However, the capability of this modality to efficiently provide samples adequate for diagnostic and prognostic analysis remains quite limited relative to current diagnostic needs. For physicians and patients, inadequate biopsy frequently leads to diagnostic delay, procedure duplication, or insufficient information about tumor biology leading to delay in treatment; for health systems, this results in substantial incremental costs and inefficient use of scarce specialized diagnostic resources.

OBJECTIVE.—

To review current needle biopsy technology, devices, and practice with a perspective to identify current limitations and opportunities for improvement in the context of advancing precision medicine.

DATA SOURCES.—

PubMed searches of fine-needle aspiration and core needle biopsy devices and similar technologies were made generally, by tissue site, and by adequacy as well as by health economics of these technologies.

CONCLUSIONS.—

Needle biopsy adequacy can be improved by recognizing the importance of this diagnostic tool by promoting common criteria for needle biopsy adequacy; by optimizing needle biopsy procedural technique, technologies, clinical practice, professional education, and quality assurance; and by bundling biopsy procedure costs with downstream diagnostic modalities to provide better accountability and incentives to improve the diagnostic process.

Current Role of Active Surveillance in the Management of a Small Renal Mass

Renal cell carcinoma accounts for 3-4% of adult malignant neoplasms and over 65,000 new cases of kidney cancer were diagnosed in the USA in 2013 [1, 2]. Widespread use of abdominal imaging is leading to an increased incidence in the detection of small renal masses (SRMs) among other causes [1-4]. In light of recent literature on the role of percutaneous renal mass biopsy and retrospective data analysis, surveillance for renal masses ≤4 cm is likely to become more common especially in patients with less aggressive pathology, advanced age and multiple medical comorbidities.

Percutaneous renal tumour biopsy

The use of percutaneous renal tumour biopsy (RTB) as a diagnostic tool for the histological characterization of renal masses has increased dramatically within the last 30 years. This increased utilization has paralleled advances in imaging techniques and an evolving knowledge of the clinical value of nephron sparing surgery. Improved biopsy techniques using image guidance, coupled with the use of smaller gauge needles has led to a decrease in complication rates. Reports from series containing a large number of cases have shown the non-diagnostic rate of RTB to range from 4% to 21%. Re-biopsy has been shown to reduce this rate, while the use of molecular markers further improves diagnostic sensitivity. In parallel with refinements of the biopsy procedure, there has been a rapid expansion in our understanding of the complexity of renal cell neoplasia. The 2013 Vancouver Classification is the current classification for renal tumours, and contains five additional entities recognized as novel forms of renal malignancy. The diagnosis of tumour morphotype on RTB is usually achievable on routine histology; however, immunohistochemical studies may be of assistance in difficult cases. The morphology of the main tumour subtypes, based upon the Vancouver Classification, is described and differentiating features are discussed.

Lessons learned from the comparative study between renal mass biopsy and the analysis of the surgical specimen

INTRODUCTION

The role of renal mass (RM) biopsy is currently under discussion. As a result of the progressive increase in the incidental diagnosis of RMs (which have a higher percentage of benignity and well-differentiated cancers), new approaches have emerged such as observation, especially with elderly patients or those with significant comorbidity. RM biopsy (RMB) should provide sufficient information for making this decision, but so far this has not been the case. We examine our prospective series of in-bench RMBs after surgery and compare them with the anatomy of the removed specimen.

MATERIAL AND METHODS

We obtained (prospectively, in-bench and with a 16-gauge needle) 4 biopsies of RMs operated on in our department from October 2008 to December 2009. These RMs were analyzed by 2 uropathologists and compared with the results of the specimen.

RESULTS

We analyzed 188 biopsies (47 RMs); 12.75% were "not valid". The ability of biopsy to diagnose malignancy or benignity was 100%, and the coincidence in the histological type was 95%. The success in determining the tumor grade was 100% when the cancer was low-grade and 62% when high-grade. None of the analyzed data (necrosis, size, etc.) influenced the results in a statistically significant manner.

CONCLUSION

RMB with a 16-G needle enables the differentiation between malignancy and benignity in 100% of cases, with a very similar diagnostic accuracy in the tumor type. Tumor grade is still the pending issue with renal mass biopsy.

Follow-up for Clinically Localized Renal Neoplasms: AUA Guideline

PURPOSE

The purpose of this guideline is to provide a clinical framework for follow-up of clinically localized renal neoplasms undergoing active surveillance, or following definitive therapy.

MATERIALS AND METHODS

A systematic literature review identified published articles in the English literature between January 1999 and 2011 relevant to key questions specified by the Panel related to kidney neoplasms and their follow-up (imaging, renal function, markers, biopsy, prognosis). Study designs consisting of clinical trials (randomized or not), observational studies (cohort, case-control, case series) and systematic reviews were included.

RESULTS

Guideline statements provided guidance for ongoing evaluation of renal function, usefulness of renal biopsy, timing/type of radiographic imaging and formulation of future research initiatives. A lack of studies precluded risk stratification beyond tumor staging; therefore, for the purposes of postoperative surveillance guidelines, patients with localized renal cancers were grouped into strata of low- and moderate- to high-risk for disease recurrence based on pathological tumor stage.

CONCLUSIONS

Evaluation for patients on active surveillance and following definitive therapy for renal neoplasms should include physical examination, renal function, serum studies and imaging and should be tailored according to recurrence risk, comorbidities and monitoring for treatment sequelae. Expert opinion determined a judicious course of monitoring/surveillance that may change in intensity as surgical/ablative therapies evolve, renal biopsy accuracy improves and more long-term follow-up data are collected. The beneficial impact of careful follow-up will also need critical evaluation as further study is completed.

Tumour-seeding: a rare complication of ablative therapy for clinically localised renal cell carcinoma

Current evidence-based clinical practice guidelines identify surgical resection as the recommended treatment of small renal masses. Ablative approaches such as laparoscopic and percutaneous cryoablation and radiofrequency ablation offer the promise of complete tumour destruction by a less-invasive approach with regard to outcomes such as anaesthesia requirements, blood loss, length of stay and time to recovery, making them appealing to patients. However, evidence of therapeutic benefits, harms and costs for these methods remains limited. We report a case of applicator tract seeding by tumour following percutaneous cryoablation of renal cell carcinoma; a rare and potentially under-reported, yet catastrophic complication of ablative therapy.

Limitations of preoperative biopsy in patients with metastatic renal cell carcinoma: comparison to surgical pathology in 405 cases

Study Type--Diagnostic (cohort) Level of Evidence: 2b. What's known on the subject? and What does the study add? Although there have been many investigations of biopsy for small renal masses, there are scant data on the accuracy of biopsy in the setting of metastatic renal cell carcinoma (mRCC). We report a large series of biopsies and compare with nephrectomy pathology in patients with mRCC. The present study highlights the inaccuracy of biopsy in the setting of metastatic disease, which is related to sampling error because of heterogeneity within the tumour and among metastases. These limitations are important to realize when designing trials that depend on pathological findings from biopsy and not nephrectomy. In addition, we found that biopsy of primary tumours were more likely than biopsy of metastatic sites to be diagnostic of RCC. Future studies with multiquadrant biopsies of primary tumours could yield the most accurate pathological results for future studies.

OBJECTIVE

• To evaluate the ability of preoperative biopsy to identify high-risk pathological features by comparing pathology from preoperative metastatic site and primary tumour biopsies with nephrectomy pathology in patients with metastatic renal cell carcinoma (mRCC).

PATIENTS AND METHODS

•  We reviewed clinical and pathological data from patients who underwent biopsy before cytoreductive nephrectomy for mRCC at MD Anderson Cancer Center (MDACC) from 1991 to 2007. • Percutaneous biopsy techniques included fine-needle aspiration, core needle biopsy or a combination of both techniques.

RESULTS

• The pathology of 405 preoperative biopsies (239 metastatic site, 166 primary tumour) from 378 patients was reviewed at MDACC before cytoreductive nephrectomy. • The biopsy and nephrectomy specimens had the same histological subtype in 96.0% of clear-cell renal cell carcinomas (RCCs) and 72.7% of non-clear-cell RCCs. • Of 76 nephrectomy specimens where sarcomatoid de-differentiation was identified, only seven (9.2%) were able to be identified from the preoperative biopsy. • In 38.3% of patients, the same Fuhrman grade was identified in both the biopsy and nephrectomy specimens. • A definitive diagnosis of RCC was more likely to be reported in primary tumour biopsies than in metastatic site biopsies. (P < 0.001).

CONCLUSIONS

• Preoperative biopsy has limited ability to identify non-clear-cell histological subtype, Fuhrman grade or sarcomatoid features. • When surgical pathology is not available, a biopsy obtaining multiple samples from different sites within the primary tumour should be recommended rather than limited metastatic site biopsy to identify patients for clinical trials.

Prevalence and predictors of benign lesions in renal masses smaller than 7 cm presumed to be renal cell carcinoma

The present study was designed to determine the incidence and predictive factors of benign renal lesions in 450 patients who underwent surgical removal of solitary renal masses <7 cm in diameter. Of the 450 renal masses, 88 (19.9%) were benign lesions. Female sex, nephron-sparing surgery, surgery between 1990 and 1996, cystic components on imaging, and small tumors (<4 cm) were independently associated with benign pathology.

PURPOSE

To determine the association between preoperative parameters with final benign pathology in patients who underwent surgical removal of solitary renal masses <7 cm in diameter.

MATERIALS AND METHODS

A database of 450 patients without metastatic disease who underwent radical nephrectomy or nephron-sparing surgery (NSS) for removal of renal masses <7 cm between January 1990 and December 2009 was reviewed. Age, sex, symptoms, year and type of surgery, solid or cystic appearance, and tumor size were analyzed as presumed predictors of benign pathology. Multivariate analysis was performed to identify parameters associated with benign pathology.

RESULTS

In all, 88 (19.9%) of the tumors were benign, including 39 (8.7%) oncocytomas and 22 (4.9%) angiomyolipomas. The benign lesion rate for tumors ≤2, 2.1-4, and 4.1-7 cm was 30.3%, 27.1%, and 12.5%, respectively (2P < .001). For the periods of 1990-1996, 1997-2003, and 2004-2009, the frequency of benign tumors was 25%, 17.3%, and 18.4% (2P = .271), the incidental tumor rate was 48.1%, 60.4%, and 63.8% (2P = .027), mean tumor size was 5, 4.6, and 4.1 cm (2P < .001), and the NSS rate was 28.8%, 43.2%, and 52.7% (2P < .001), respectively. Logistic regression analysis revealed that female sex, NSS, surgery between 1990 and 1996, cystic components on imaging, and small tumors (<4 cm) based on radiologic examination were independently associated with benign pathology (odds ratio [OR] = 3.26, 2.56, 2.43, 2.41, and 1.96, respectively).

CONCLUSIONS

The incidence of incidental and small tumors amenable to NSS increased over time. Female sex was the strongest predictor of benign pathology.

The penetration of renal mass biopsy in daily practice: a survey among urologists

BACKGROUND AND PURPOSE

The vast increase in recent publications on renal mass biopsy (RMB) suggests an increased interest in the subject. The objective of the survey was to assess the use of RMB in current urologic practice, including related factors such as indications and patterns in practice.

METHODS

The link to a web-based questionnaire ( www.surveymonkey.com ) was sent to all registered e-mail addresses (1854) of members of the Endourological Society in December 2010. The questionnaire contained six epidemiologic questions, 10 regarding patterns of practice, one regarding the influence of the literature, and one on future techniques. Chi-square test (for trends) was used to assess statistical significant differences among categorical answers.

RESULTS

In total, 190 responders completed the survey of whom 73% indicated performing RMB "never" or "rarely" compared with 9% performing RMB in 25% to 100% of cases. Thirteen percent of responders reported never to take a RMB. Of the latter, significantly fewer practice in university hospitals (6% vs 20%-30%, P=0.003). Main indications to perform RMB are still tumors in solitary/transplant kidneys and in metastatic disease. Lack of influence on clinical management and risk of false negatives were the main reasons not to perform biopsies. Sixty-one percent prefer histological biopsies compared with 8% who prefer cytological aspiration; 31% indicated that they combine both techniques. Other tissue differentiation techniques (Optical Coherence Tomography, Raman-spectroscopy) are unknown to 65% of urologists.

CONCLUSION

RMB is not yet applied widely in urologic practice, with academic urologists performing RMB less infrequently. Core biopsies are still preferred, although combined with cytologic punctures by a considerable number of responders.

Evaluation of renal masses with contrast-enhanced ultrasound: initial experience

OBJECTIVE

Nearly 25% of solid renal tumors are indolent cancer or benign and can be managed conservatively in selected patients. This prospective study was performed to determine whether preoperative IV microbubble contrast-enhanced ultrasound can be used to differentiate indolent and benign renal tumors from more aggressive clear cell carcinoma.

SUBJECTS AND METHODS

Thirty-four patients with renal tumors underwent preoperative gray-scale, color, power Doppler, and octafluoropropane microbubble IV contrast-enhanced ultrasound. Three blinded radiologists reading in consensus compared rate of contrast wash-in, grade and pattern of enhancement, and contrast washout compared with adjacent parenchyma. Contrast ultrasound findings were compared with surgical histopathologic findings for all patients.

RESULTS

The 34 patients had 23 clear cell carcinomas, three type 1 papillary carcinomas, one chromophobe carcinoma, one clear rare multilocular low-grade malignant tumor, two unclassified lesions, three oncocytomas, and one benign angiomyolipoma. The combination of heterogeneous lesion echotexture and delayed lesion washout had 85% positive predictive value, 43% negative predictive value, 48% sensitivity, and 82% specificity for predicting whether a lesion was conventional clear cell carcinoma or another tumor. Diminished lesion enhancement grade had 75% positive predictive value, 81% negative predictive value, 55% sensitivity, and 91% specificity for non-clear cell histologic features, either benign or low-grade malignant. Combining delayed washout with quantitative lesion peak intensity of at least 20% of kidney peak intensity had 91% positive predictive value, 40% negative predictive value, 63% sensitivity, and 80% specificity in the prediction of clear cell histologic features.

CONCLUSION

Ultrasound features of gray-scale heterogeneity, lesion washout, grade of contrast enhancement, and quantitative measure of peak intensity may be useful for differentiating clear cell carcinoma and non-clear cell renal tumors.

Small renal mass: what the urologist needs to know for treatment planning and assessment of treatment results

OBJECTIVE

Small renal mass is a new distinct clinical entity. Detection of these tumors has increased with increased use of imaging.

CONCLUSION

We know that a proportion of these tumors are not renal cell carcinoma, and imaging-guided biopsy is being increasingly used for treatment planning. The objectives of this review are to provide an update on our current understanding of the biology of small renal masses and to review approaches to the diagnosis and treatment of these lesions.

The impact of germline BHD mutation on histological concordance and clinical treatment of patients with bilateral renal masses and known unilateral oncocytoma

PURPOSE

Managing oncocytoma in the setting of bilateral renal masses is a challenging scenario. Nevertheless, to our knowledge the pathological concordance of an oncocytic neoplasm in 1 kidney with tumors in the contralateral kidney is not known. We evaluated the influence of germline Birt-Hogg-Dubé mutation on concordance rates to assist in managing these cases.

MATERIALS AND METHODS

We reviewed the records of patients at the National Institutes of Health between 1983 and 2009 who had bilateral renal masses, known pathology bilaterally and oncocytoma or an oncocytic neoplasm in at least 1 kidney. Oncocytoma or an oncocytic neoplasm in 2 renal units was considered concordant. Demographic, pathological and clinical data were collected.

RESULTS

The population consisted of 40 patients, including 23 with and 17 without a diagnosis of Birt-Hogg-Dubé syndrome. Patients with the syndrome were younger (p <0.01) but there were no other differences between the 2 groups. However, patients with the syndrome had statistically lower histological concordance between bilateral masses than patients without the diagnosis (Fisher's exact test p <0.01). Also, the 8 patients without Birt-Hogg-Dubé syndrome who had multifocal renal masses showed 100% oncocytoma concordance between renal units.

CONCLUSIONS

Of patients with bilateral renal masses those with Birt-Hogg-Dubé syndrome have significantly lower histological concordance than those without the syndrome. Patients with Birt-Hogg-Dubé syndrome should be monitored and treated differently than those without detected genetic mutations, especially patients with multifocal oncocytomas. Genetic testing for Birt-Hogg-Dubé should be considered in the treatment algorithm of patients with bilateral renal masses and known oncocytoma.

What is the added value of combined core biopsy and fine needle aspiration in the diagnostic process of renal tumours?

PURPOSE

Non-diagnostic results still hinder the routine use of core biopsy (CB) and fine needle aspiration (FNA) in the diagnostic process of renal tumours. Furthermore, substantial interobserver variability has been reported. We assessed the added value of combining the results of CB and FNA by five pathologists in the ex vivo diagnosis of renal mass.

METHODS

Two ex vivo core biopsies were taken followed by two FNA passes from extirpated tumours. All samples were evaluated by five blinded pathologists. A consensus diagnosis of the surgical specimen was the index for comparison. For each pathologist, the number of non-diagnostic (non-conclusive or undetermined biology and failed biopsies), correct and incorrect scored cases of each technique was assessed. When a non-diagnostic CB or FNA had a correct diagnostic counterpart, this was considered as of added value.

RESULTS

Of the 57 assessed tumours, 53 were malignant. CB was non-diagnostic in 4-10 cases (7-17.5%). FNA established the correct diagnosis in 1-7 of these cases. FNA was non-diagnostic in 2-6 cases (3.5-10.5%), and the counterpart CB established the correct diagnosis in 1-6 of these cases. For the 5 pathologists, accuracy of CB and FNA varied between 82.5-93% and 89.5-96.5%, respectively. Combination of both types of biopsy resulted in 55-57 correct results (accuracy 96.5-100%), i.e., an increase in accuracy of 3.5-14%.

CONCLUSION

Combining the result of CB and FNA in renal mass biopsy leads to a higher diagnostic accuracy. Recommendations on which technique used should be adapted to local expertise and logistic possibilities.

A technical note: pre-operative ultrasound-guided wire localization in head and neck surgery

Ultrasound-guided wire localization of impalpable lesions is a well-recognized technique in the management of breast pathology, but its use in the head and neck is not well described. Performed under local anesthesia, high-resolution ultrasound provides real-time imaging for accurate placement of the wire resulting in fewer complications. Wire localization can focus the surgical approach, which reduces operating time and minimizes trauma to surrounding tissues. In this technical note, we describe two cases of pre-operative ultrasound-guided wire localization to facilitate the surgical excision of impalpable neck lesions.

Advanced diagnostics in renal mass using optical coherence tomography: a preliminary report

OBJECTIVE

To avoid unnecessary surgical treatment of small renal masses (≤ 4 cm), a more accurate diagnostic method would be desirable since radiological differentiation between malignant and benign is difficult and nondiagnostic biopsies account from 9% to 37%. Optical coherence tomography (OCT) measures backscattered light versus depth, with an attenuation coefficient (μ(t)) that may vary among different histological types. We hypothesize that quantitative measurements of μ(t) using OCT can differentiate between normal renal parenchyma and renal cell carcinoma (RCC).

MATERIALS AND METHODS

Both normal and tumor renal tissues (RCC) were harvested after partial or radical nephrectomy. Analysis of μ(t) was based on difference of (1) μ(t) between normal and tumor tissue across all patients and (2) μ(t) between normal and tumor tissue within individual patients.

RESULTS

Tissue samples of 18 patients were measured, of which 4 were excluded (urothelial carcinoma, oncocytoma, and benign lesion without normal tissue available). Of the remaining 14 patients, 8 contributed with both normal and RCC tissue and 6 with only normal or RCC tissue. Independent observation showed a significant difference between the median μ(t) of normal renal tissue (4.95 mm⁻¹) and the median μ(t) of RCC (8.86 mm⁻¹). No statistically significant difference was found when comparing the difference in μ(t) between normal renal parenchyma and RCC within individual patients.

CONCLUSION

There is a significant difference in μ(t) between normal and RCC tissue across all patients. These results overpower the lack of significant difference within individuals, encouraging further research and suggesting a possible role for OCT in the diagnostic work-up of renal masses.

Renal mass sampling: an enlightened perspective

Renal mass sampling (RMS) can be carried out by core biopsy or fine needle aspiration with each presenting potential advantages and limitations. The literature about RMS is confounded by a lack of standardized techniques, ambiguous terminology, imprecise definitions of accuracy, substantial rates of non-informative biopsies, and recurrent diagnostic challenges with respect to eosinophilic neoplasms. Despite these concerns, RMS has an expanding role in the evaluation and treatment of renal masses, in order to stratify biological aggressiveness and guide management that can range from surgery to active surveillance. Non-informative biopsies can be managed with surgical excision or repeat biopsy, with the latter showing encouraging results in recent studies. We propose a new classification in which all biopsies are categorized as non-informative versus informative, with the latter being subclassified as confirmed accurate, presumed accurate or confirmed inaccurate. This terminology will facilitate the comparison of results from various studies and stimulate progress. Incorporation of novel biomarkers and molecular fingerprinting into RMS protocols will likely allow for more rational management of patients with renal masses in the near future.