Percutaneous Kidney Biopsy for a Small Renal Mass: A Critical Appraisal of Results

The evolving management of small renal masses

Small renal masses (SRMs) are a heterogeneous group of tumours with varying metastatic potential. The increasing use and improving quality of abdominal imaging have led to increasingly early diagnosis of incidental SRMs that are asymptomatic and organ confined. Despite improvements in imaging and the growing use of renal mass biopsy, diagnosis of malignancy before treatment remains challenging. Management of SRMs has shifted away from radical nephrectomy, with active surveillance and nephron-sparing surgery taking over as the primary modalities of treatment. The optimal treatment strategy for SRMs continues to evolve as factors affecting short-term and long-term outcomes in this patient cohort are elucidated through studies from prospective data registries. Evidence from rapidly evolving research in biomarkers, imaging modalities, and machine learning shows promise in improving understanding of the biology and management of this patient cohort.

Radiomics Machine Learning Analysis of Clear Cell Renal Cell Carcinoma for Tumour Grade Prediction Based on Intra-Tumoural Sub-Region Heterogeneity

BACKGROUND

Renal cancers are among the top ten causes of cancer-specific mortality, of which the ccRCC subtype is responsible for most cases. The grading of ccRCC is important in determining tumour aggressiveness and clinical management.

OBJECTIVES

The objectives of this research were to predict the WHO/ISUP grade of ccRCC pre-operatively and characterise the heterogeneity of tumour sub-regions using radiomics and ML models, including comparison with pre-operative biopsy-determined grading in a sub-group.

METHODS

Data were obtained from multiple institutions across two countries, including 391 patients with pathologically proven ccRCC. For analysis, the data were separated into four cohorts. Cohorts 1 and 2 included data from the respective institutions from the two countries, cohort 3 was the combined data from both cohort 1 and 2, and cohort 4 was a subset of cohort 1, for which both the biopsy and subsequent histology from resection (partial or total nephrectomy) were available. 3D image segmentation was carried out to derive a voxel of interest (VOI) mask. Radiomics features were then extracted from the contrast-enhanced images, and the data were normalised. The Pearson correlation coefficient and the XGBoost model were used to reduce the dimensionality of the features. Thereafter, 11 ML algorithms were implemented for the purpose of predicting the ccRCC grade and characterising the heterogeneity of sub-regions in the tumours.

RESULTS

For cohort 1, the 50% tumour core and 25% tumour periphery exhibited the best performance, with an average AUC of 77.9% and 78.6%, respectively. The 50% tumour core presented the highest performance in cohorts 2 and 3, with average AUC values of 87.6% and 76.9%, respectively. With the 25% periphery, cohort 4 showed AUC values of 95.0% and 80.0% for grade prediction when using internal and external validation, respectively, while biopsy histology had an AUC of 31.0% for the classification with the final grade of resection histology as a reference standard. The CatBoost classifier was the best for each of the four cohorts with an average AUC of 80.0%, 86.5%, 77.0% and 90.3% for cohorts 1, 2, 3 and 4 respectively.

CONCLUSIONS

Radiomics signatures combined with ML have the potential to predict the WHO/ISUP grade of ccRCC with superior performance, when compared to pre-operative biopsy. Moreover, tumour sub-regions contain useful information that should be analysed independently when determining the tumour grade. Therefore, it is possible to distinguish the grade of ccRCC pre-operatively to improve patient care and management.

The success rate of small renal mass core needle biopsy and its impact on lowering benign resection rate

BACKGROUND

Small renal mass (SRM) biopsy remains under-utilized due to stigma. Meanwhile, the alarmingly high benign findings in resected kidney masses highlight the need for improved preoperative diagnosis and patient selection.

METHODS

The purpose of this study is to review the success rate of SRM biopsy and to evaluate its impact on patient management. A total of 168 percutaneous image-guided core needle biopsies (CNBs) of SRMs were retrieved at a tertiary academic center between 2015 and 2019. Subsequent treatment choices, side effects and outcomes were retrospectively reviewed.

RESULTS

The diagnostic rate of CNB was 86.9%. Benign neoplasms accounted for a significant portion (14.3%) of SRM. Renal cell carcinomas (RCCs) were the most common diagnoses (69.6%) as expected. In biopsy-resection correlation, the positive predictive value of CNB was 100%. Tumor typing and subtyping by CNB were highly accurate, 100% and 98.3% respectively. Nuclear grading for clear cell RCC was accurate in 83.8% cases. The CNB results had significant impact on treatment. Most patients with RCCs underwent either resection (54.1%) or ablation (33.9%), in contrast to observation in benign neoplasms (90.5%). Most importantly, the benign resection rate (3.2%) in this series was much lower than the national average.

CONCLUSION

CNB provided accurate diagnoses for the majority of SRMs and revealed benign diagnoses in a subset of clinically suspicious lesions. Employment of CNB in suspicious SRM may help avoid overtreatment for benign lesions.

Diagnostic accuracy of percutaneous core biopsy before cryoablation for small-sized renal cell carcinoma

PURPOSE

To retrospectively determine the diagnostic accuracy of a percutaneous core biopsy performed before cryoablation for small-sized renal cell carcinoma.

METHODS

In this study, 216 patients underwent a percutaneous core biopsy for 242 renal lesions suspected to be renal cell carcinoma on image findings before cryoablation at Kyushu University Hospital. We calculated the success rate of the histological diagnosis and investigated factors that may have contributed to the diagnostic success. Complications caused by the biopsy procedure were also evaluated.

RESULTS

The histological diagnosis was successful in 203 lesions (82.8%). The success rate of the histological diagnosis was 65.4% (34/52 cases) for tumors with a diameter of ≤15 mm and 88.9% (169/190 cases) for those >15 mm. Therefore, tumor diameter was a factor contributing to the histological diagnosis success rate in both univariate and multivariable analyses (P < 0.001). For lesions with a tumor diameter ≤15 mm, the histological diagnosis success rates increased from 50.0% to 76.2% in the presence of pre-lipiodol marking and to 85.7% when the biopsy procedure was performed separately from cryoablation; the latter was statistically significant (P = 0.039). Major complications that may have been caused by the biopsy procedure were grade 3 bleeding and tract seeding (one case each).

CONCLUSION

Percutaneous core biopsy in cryoablation for small-sized renal cell carcinoma had a high diagnostic rate and was safely performed. For lesions with a tumor diameter ≤15 mm, a separate biopsy procedure and pre-lipiodol marking may improve the diagnostic accuracy.

Diagnosing Oncocytoma by Core Needle Biopsy: A Single-Center Experience

Background

Oncocytoma is one of the most common benign kidney tumors, accounting for 3–7% of all solid renal masses. Diagnosing oncocytomas using renal biopsy remains a controversy in the uro-pathologic community. With the increasing use of biopsies for assessment of renal lesions, reaching this pathologically benign diagnosis may prevent further surgical measures and have significant clinical benefit.

Objective

To demonstrate our center's results using renal biopsy to diagnose oncocytomas and to suggest that this diagnosis can be made with high success rates.

Design

, Setting, and Participants. From our center's database, we retrospectively identified and retrieved all cases of oncocytoma diagnosed between the years 2011 and 2020 by renal biopsy. Medical records of those patients were then reviewed to view follow-up meetings and imaging of the lesions biopsied. Outcome Measurements and Statistical Analysis. In 21 biopsies performed on 19 patients, diagnosis was supported by subsequent follow-up averaging at 3.44 years per patient. Results and Limitations. The lesions exhibited benign behavior during follow-up after biopsy, consistent with the diagnosis of oncocytoma.

Conclusions

Our study demonstrates that with good patient selection and proficient cooperation between urologists, radiologists and dedicated uro-pathologists, correctly diagnosing oncocytomas using RCB is a viable task. Patient Summary. Oncocytomas are benign lesions of the kidney. In our study, we reviewed all cases of oncocytomas pathologically diagnosed using renal biopsy from our center's database. We found that in subsequent follow-up later to biopsy, the lesions displayed benign behavior consistent with oncocytoma. The use of percutaneous biopsies to reach this diagnosis could save patients more extensive surgeries.

Percutaneous biopsy of small renal mass: can diagnostic accuracy be affected by hospital volume?

Introduction

High diagnostic performance and low morbidity for renal tumor biopsy (RTB) have been described in highly experienced centers. Here we present the five-year experience of our institute in performing RTB. The protocol used, the safety profile and the diagnostic accuracy obtained were analyzed.

Material and methods

The study is a retrospective single-institution clinical data review of 84 consecutive RTB of small renal masses. Post-biopsy complications were reported using the Clavien-Dindo system. To measure the concordance between biopsy and nephrectomy specimens regarding histological subtype and International Society of Urological Pathology/World Health Organization (ISUP/WHO) renal cell carcinoma grade, the kappa coefficient of Cohen was used.

Results

Median (IQR) follow-up time was 44 (29–58) months. In total, 94% of RTB procedures were free of complications; when complications did occur, 80% were grade I and 20% were grade II. No cases of tumor seeding were observed. Combining the first and repeated biopsies the overall diagnostic rate was 85.8%. Overall, 79.1% of diagnostic RTB were malignant. In 42 surgically treated patients, the concordance between the histological results of biopsies and surgical specimens was very good for histological subtypes (k = 0.87) and moderate for tumor grade (k = 0.51).

Conclusions

RTB resulted in a high safety profile. The overall diagnostic rate was 85% and an unnecessary intervention was avoided in 21% of patients. RTB showed a very good accuracy in determining the histological subtype of renal cancer while it was moderate for the tumor grade. These results are similar to those reported in larger series and support feasibility of this procedure in low-volume centers.

Ultrasound-guided percutaneous renal biopsy at a university hospital: retrospective analysis of success and complication rates

OBJECTIVE

To evaluate the success and complication rates of ultrasound-guided renal biopsy at a tertiary care hospital.

MATERIALS AND METHODS

This was a retrospective analysis of 97 ultrasound-guided renal biopsies, all performed by the same radiologist, between 1 March, 2017 and 31 October, 2019.

RESULTS

Of the 97 biopsies evaluated, 87 had a definitive pathological diagnosis. In five cases (5.4%), the biopsy results were inconclusive and a second procedure was required. In seven procedures (7.6%), there were complications, all of which were properly resolved.

CONCLUSION

Ultrasound-guided renal biopsy has proven to be a safe, effective method for the diagnosis of nephropathies, with high success rates.

Learnable image histograms-based deep radiomics for renal cell carcinoma grading and staging

Fuhrman cancer grading and tumor-node-metastasis (TNM) cancer staging systems are typically used by clinicians in the treatment planning of renal cell carcinoma (RCC), a common cancer in men and women worldwide. Pathologists typically use percutaneous renal biopsy for RCC grading, while staging is performed by volumetric medical image analysis before renal surgery. Recent studies suggest that clinicians can effectively perform these classification tasks non-invasively by analyzing image texture features of RCC from computed tomography (CT) data. However, image feature identification for RCC grading and staging often relies on laborious manual processes, which is error prone and time-intensive. To address this challenge, this paper proposes a learnable image histogram in the deep neural network framework that can learn task-specific image histograms with variable bin centers and widths. The proposed approach enables learning statistical context features from raw medical data, which cannot be performed by a conventional convolutional neural network (CNN). The linear basis function of our learnable image histogram is piece-wise differentiable, enabling back-propagating errors to update the variable bin centers and widths during training. This novel approach can segregate the CT textures of an RCC in different intensity spectra, which enables efficient Fuhrman low (I/II) and high (III/IV) grading as well as RCC low (I/II) and high (III/IV) staging. The proposed method is validated on a clinical CT dataset of 159 patients from The Cancer Imaging Archive (TCIA) database, and it demonstrates 80% and 83% accuracy in RCC grading and staging, respectively.

Diagnostic renal mass biopsy is associated with individual categories of PADUA and RENAL nephrometry scores: Analysis of diagnostic and concordance rates with surgical resection

BACKGROUND

Renal mass biopsy (RMB) is a safe and accurate method for diagnosis and clinical management of renal masses. However, the non-diagnostic rate is a limiting factor. We tested the hypothesis that imaging characteristics and anatomic complexity of the mass may impact RMB diagnostic outcome using the preoperative aspects and dimensions used for an anatomical (PADUA) classification and radius-exophytic/endophytic-nearness-anterior/posterior-location (RENAL) score.

MATERIAL AND METHODS

Single institution, retrospective study of 490 renal masses from 443 patients collected from 2001 to 2018. Outcome measurements include (1) diagnostic and concordance rates amongst RMB types and RMB with surgical resection specimens; (2) association between diagnostic RMB and anatomical complexity of renal masses. The analysis was conducted in unselected masses and small renal masses (SRMs).

RESULTS

RMB was performed by fine needle aspiration (FNA), core needle biopsy (CNB), or both (FNA+CNB). Non-diagnostic rate was significantly higher for FNA compared to CNB and FNA+CNB in both unselected and SRMs. Subset analysis in the FNA+CNB group showed similar diagnostic rates for FNA and CNB. In unselected masses, specificity for FNA, CNB, and FNA+CNB was 100%. Sensitivity was higher for CNB (90.1%, P = 0.002) and FNA+CNB (96.3%, P = 0.004) compared to FNA (66.7%). For unselected masses, endophytic growth predicted a non-diagnostic CNB. R.E.N.A.L location entirely between the polar lines (central) and entirely above the upper polar line predicted a diagnostic CNB. Sonography-guidance predicted a diagnostic FNA. For SRMs, non-diagnostic CNB was associated with endophytic growth, while diagnostic CNB was associated with renal sinus invasion and operator experience. More cystic masses were sampled by FNA, but diagnostic results were similar for FNA and CNB.

CONCLUSIONS

Endophytic growth consistently predicted a non-diagnostic CNB in unselected and SRMs, whereas sonography-guidance predicted a diagnostic FNA. Cystic masses could be adequately sampled by FNA.

Prevalence of benign pathology after partial nephrectomy for suspected renal tumor: A systematic review and meta-analysis

OBJECTIVE

To investigate the overall prevalence of benign pathology after partial nephrectomy (PN) and identify predictive factors for benign pathology after PN.

METHODS

A systematic review was performed following the PRISMA guidelines. PubMed/Medline, Embase, and the Cochrane Library were searched up to January 2019PRISMA guidelines. The data for the meta-analysis and network meta-analysis were pooled using a random-effects model.

RESULTS

There were 144 studies included in the final analysis, which was comprised of 79 observational studies (n = 37,300) and 65 comparative studies (n = 18,552). The overall prevalence rate of benign pathology after PN was 0.19 (95% CI: 0.18-0.21). According to the procedure types, the prevalence rate of benign pathology was 0.17 (95% CI: 0.15-0.19), 0.24 (95% CI: 0.22-0.27), and 0.16 (95% CI: 0.15-0.18) in open partial nephrectomy, laparoscopic partial nephrectomy, and robot-assisted laparoscopic partial nephrectomy, respectively. The significant moderating factors were gender, publication year, the origin of the study, and procedure types. The three most common benign pathology types were oncocytomas, angiomyolipomas, and renal cysts (44.50%, 30.20%, and 10.99%, respectively).

CONCLUSIONS

The overall prevalence of benign pathology after PN was not low and it was affected by female gender, studies published before 2010, studies originating from Western areas, and laparoscopic procedure types.

Computed tomography-guided biopsy for small renal masses before or immediately after tumor ablation: factors affecting diagnostic yield

PURPOSE

To evaluate the diagnostic yield of percutaneous renal mass biopsy (RMB) before and after ablation.

MATERIALS AND METHODS

In total, 333 renal masses in 332 consecutive patients underwent computed tomography (CT)-guided biopsies and were included in this study. All biopsies were performed with 18-gauge core needles with CT fluoroscopic guidance before ablation (n  =  234) or immediately after radiofrequency ablation (RFA) (n  =  40) or cryoablation (CA) (n  =  59). The safety and diagnostic yield of RMB were evaluated. Both univariate and multivariate analyses were used to identify factors affecting diagnostic yield.

RESULTS

No major complication occurred. The 281 specimens (84%) were diagnostic. There were 257 renal cell carcinomas (77%), 21 benign masses (6%), and 3 metastases (1%). The remaining 52 specimens (16%) were nondiagnostic. The diagnostic yields before ablation, after RFA, and CA were 91% (212/234), 80% (32/40), and 63% (37/59), respectively. Small masses (P  =  0.050 and 0.006), cystic masses (P < 0.001 and < 0.001), and post-CA (P < 0.001 and < 0.001) were independent and significant factors affecting the nondiagnostic results in both univariate and multivariate analyses.

CONCLUSION

CT-guided RMB can be nondiagnostic when the tumor is small, cystic, or biopsied immediately after CA.

Contemporary Results and Clinical Utility of Renal Mass Biopsies in the Setting of Ablative Therapy: A single center experience

PURPOSE

Clinical guidelines have recently included renal mass biopsy (RMB) in management algorithms, especially in the setting of small renal masses ≤ 4 cm (SRM) and ablative therapy. We sought to evaluate the diagnostic rates of RMB, factors associated with a non-diagnostic biopsy, its clinical utility, and its safety profile in the setting of ablative therapy.

MATERIALS AND METHODS

A total of 174 RMB from 167 patients, performed in a tertiary academic center from 01/2015 to 01/2019, were included. Patient demographics, radiographic mass size, RMB diagnoses, subsequent clinical management, and complications were retrospectively reviewed. RMBs were classified as diagnostic or non-diagnostic based on set criteria.

RESULTS

The mean mass size was 3.0 cm (range: 0.5-15.3 cm) and 140 biopsies (80%) were SRM. Among all RMB, 159 (91%) were diagnostic and 15 (9%) were non-diagnostic. Non-diagnostic biopsies were associated with small mass size, the presence of a cystic component (p < 0.00001) and fewer number of cores submitted (p = 0.0046). All non-diagnostic biopsies occurred in SRMs, where the mean mass size was significantly smaller than diagnostic biopsies (1.3 versus 3.2 cm, p = 0.001). RMB with concurrent ablation yielded non-diagnostic results more frequently than isolated RMBs (15% vs 2%, respectively).

CONCLUSIONS

RMB is useful for definitive diagnosis and clinical management in the setting of ablative therapy. Small mass size, cystic lesions, and fewer number of passes obtained are associated with non-diagnostic biopsies. When a renal mass diagnosis is particularly critical, a separate biopsy procedure prior to ablative therapy is recommended.

The role of percutaneous fine needle aspiration biopsy in the management of small renal masses without chance of nephron-sparing surgery

PURPOSE

We seek to confirm the safety and efficacy of percutaneous fine needle aspiration biopsy (FNAB) for small renal masses (SRMs) without chance of nephron-sparing surgery (NSS).

METHODS

Between 2015 and 2018, 169 consecutive patients with SRMs treated in two medical centers were enrolled in the study retrospectively. All patients were evaluated to be candidates of radical nephrectomy (RN) at the initial evaluation preoperatively and they would receive the second evaluation in operation to decide the ultimate surgical regimen. Patients were divided into two groups according to FNAB.

RESULTS

169 patients met inclusion criteria were enrolled in the finial study. The median follow-up of was 35 months (ranges from 23 to 49 months) from the first diagnosis. 83 patients received FNAB before surgery, and the other 86 patients underwent surgery immediately. The initial success rate of FNAB was 91.6% (76/83) and the rate of accuracy in identifying malignancies was 100%. 15 (18.1%) of 83 patients developed different levels of complications. 15 (18.1%) were diagnosed as benign tumors by FNAB. The initial success rate was just 50% for cystic SRMs. Complicated cystic SRMs account for 5.9% of all with a 50% benignity rate. The FNAB group had a significant lower ratio of RN than non-FNAB group (74.7% vs. 93%, p = 0.001, Pearson Chi-square test).

CONCLUSION

FNAB is safe and effective for SRMs without chance of NSS, and it could significantly reduce unnecessary RN.

Identification of tumor size as the only factor associated with nondiagnostic biopsies in patients with small renal masses

INTRODUCTION

As greater numbers of small renal masses (SRMs) are discovered incidentally, renal tumor biopsy (RTB) is an increasingly recognized step for the management of these lesions, ideally for the prevention of surgical overtreatment for benign disease. While the diagnosis can often be obtained preoperatively by RTB, indeterminate results create greater difficulty for patients and clinicians. This study examines a series of RTBs, identifying the portion of these that were able to yield a diagnosis, and correlates patient factors, including RENAL and PADUA scoring, with the outcome of a non-diagnostic result.

METHODS

Patients were identified as having undergone RTB at the Princess Margaret Cancer Centre in Ontario, Canada, between January 2000 and December 2009. Data was compiled from these 423 patients and analyzed using CART methodology to determine the level of association between various patient and tumor factors and the outcome of a non-diagnostic biopsy. Tumor size was further used to develop a classification tree to describe the prediction of a non-diagnostic biopsy.

RESULTS

Of these 423 patients undergoing RTB, 66 (16%) resulted in a non-diagnostic biopsy. The only patient or tumor factor that was found to be associated with a non-diagnostic outcome was mass size, where small masses (<1.28 cm diameter) were found to have a 38% chance of being non-diagnostic, compared with a 13% chance in those tumors >1.28 cm diameter (86% accuracy, 95% confidence interval [CI] 0.82-0.89).

CONCLUSIONS

When evaluating SRMs for diagnostic workup, mass size is the only tumor or patient characteristic associated with a non-diagnostic RTB.

The role of renal biopsy to improve small renal mass diagnosis and management: are there predictive factors for a higher detection rate? The first Italian study of 100 cases

BACKGROUND

Incidence of small renal masses (SRMs) has increased over the last decade: in order to reduce overtreatment of benign lesions, renal tumor biopsy (RTB) has been advocated. The primary aim of this study were to establish the rate of diagnostic biopsies and the concordance rate between RTB and surgical pathology with regard to tumor histology. The secondary aim was to identify what predictive factors are associated with an initial diagnostic biopsy.

METHODS

We retrospectively analyzed RTB performed in our center in patients with SRMs between 2015 and 2017. We assessed patient demographics and clinical status, lesion characteristics and procedural factors. The categorical variables were tested with the chi-square test. We used univariate and multivariate analysis to identify what factors are indicative of non-diagnostic biopsies. We used the SPSS statistics v. 23.

RESULTS

We performed a total of 100 RTBs to management 94 patients. The initial biopsy was diagnostic in 88 patients (67 malignant and 21 benign lesion). The six remaining patients had repeat biopsies, of which four were diagnostic. Complications rate was 5% prevalently local hematoma treated with surveillance. Agreement between biopsy and surgical histology was found in 94% of cases. On contingency analysis and on univariate and multivariate analysis, these factors (age, tumor size, exophytic location, and type of imaging used) were not predictive with diagnostic biopsy.

CONCLUSIONS

RTB for SRMs helps establish pre-treatment diagnosis, reduce overtreatment, with a low risk of complications and high diagnostic rate. In our experience, we did not find predictive factors more likely associated with a diagnostic biopsy.

Development and validation of CT imaging-based preoperative nomogram in the prediction of unfavorable high-grade small renal masses

PURPOSE

In recent years, there has been an increase in the incidence of small renal masses (SRMs) and nephrectomy was the standard management of this disease in the past. Currently, the use of active surveillance has been recommended as an alternative option in the case of some patients with SRMs due to its heterogenicity. However, limited studies focused on the regarding risk stratification. Therefore, in the current study, we developed a nomogram for the purpose of predicting the presence of high-grade SRMs on the basis of the patient information provided (clinical information, hematological indicators, and CT imaging data).

PATIENTS AND METHODS

A total of 329 patients (consisting of development and validation cohort) who had undergone nephrectomy for SRMs between January 2013 and May 2016 retrospectively were recruited for the present study. All preoperative information, including clinical predictors, hematological indicators, and CT predictors, were obtained. Lasso regression model was used for data dimension reduction and feature selection. Multivariable logistic regression analysis was applied for the establishment of the predicting model. The performance of the nomogram was assessed with respect to its calibration and discrimination properties and externally validated.

RESULTS

The predictors used in the assessment of the nomogram included tumor size, CT tumor contour, CT necrosis, CT tumor exophytic properties, and CT collecting system oppression. Based on these parameters, the nomogram was evaluated to have an effective discrimination and calibration ability, and the C-index was found to be 0.883 after internal validation and 0.887 following external validation.

CONCLUSION

Based on the aforementioned findings, it can be concluded that CT imaging-based preoperative nomogram is an effective predictor of SRMs and hence can be used in the preoperative evaluation of SRMs, due to its calibration and discrimination abilities.

Percutaneous image-guided renal ablations: Current evidences for long-term oncologic efficacy

The rise in incidentally discovered small renal neoplasms has focused attention on nephron-sparing treatment strategies including partial nephrectomy and percutaneous ablation as well as active surveillance. As all treatment modality, renal ablation has matured technically. Radiofrequency ablation, microwave ablation or cryoablation are now performed in many institutions under imaging guidance. The long-term results allow them to be now recommended as a therapeutic option whatever the patients' condition if complete ablation can reliably be achieved.

Percutaneous renal biopsy: approach, diagnostic accuracy and risks

PURPOSE OF REVIEW

This article provides a review of recent advances and issues regarding the controversial topic of renal mass biopsy (RMB). The purpose of this review is to provide an update on the current status of renal biopsy based on recently published literature. Here, we particularly focus on articles that have been published within the last 12 months.

RECENT FINDINGS

The main topics covered in this review are the approach, diagnostic accuracy and risks related to RMB.

SUMMARY

Current literature suggests that improvements in both technique and technological advancements of RMB have led to greater diagnostic accuracy and low risks to the patient. Newer technologies are leading toward innovative and harmless ways to diagnose kidney cancer, including liquid and image-based biopsy. However, it appears that the question of whether or not to instate renal biopsy as standard clinical practice has remained a highly debated controversy.

An Integrated Score and Nomogram Combining Clinical and Immunohistochemistry Factors to Predict High ISUP Grade Clear Cell Renal Cell Carcinoma

Objective: The International Society of Urological Pathology (ISUP) has proposed a grading system to classify renal cell carcinoma (RCC). However, classification using biopsy specimens remains problematic and, consequently, the accuracy of a biopsy-based diagnosis is relatively poor. This study aims to combine clinical and immunohistochemical (IHC) factors for the prediction of high ISUP grade clear cell RCC (ccRCC) in an attempt to complement and improve the accuracy of a biopsy-based diagnosis. Methods: A total of 362 ccRCC patients were enrolled in this study and used for the training set. We performed IHC analysis of 18 protein markers on standard tissue sections using an automated stainer. Multivariate logistic regression models were developed to evaluate independent predictors for high ISUP grade. We evaluated different prediction models using receiver operating characteristic (ROC) curves and area under the ROC curve (AUC) analysis. A nomogram for the derivation of an integrated score for predicting high ISUP grade ccRCC and a calibration curve were also plotted. Finally, an internal validation cohort was examined to evaluate the performance of our integrated scoring system and nomogram. Results: Multivariate logistic analyses revealed seven credible candidates for predicting high grade ISUP. These were age, tumor diameter, surgery, and CK7, Ki-67, PTEN, and MTOR protein expression. The ROC curves for the clinical, IHC and integrated models were compared in the training set, and the AUC for each was 0.731, 0.744, and 0.801, respectively. DeLong's test showed that the integrated model was significantly better at predicting high ISUP grade, when compared with the other models. Internal validation confirmed the good performance of the integrated score in predicting ISUP grade. Conclusion: We have developed a nomogram integrating clinical and immunohistochemical parameters to predict high ISUP grade for M0 ccRCC patients. This nomogram may offer potentially useful information during preoperative individualized patient risk assessment, and consequently may help urologists when planning personalized management regimens.

WHO/ISUP classification, grading and pathological staging of renal cell carcinoma: standards and controversies

PURPOSE

Pathological parameters assessed on biopsies and resection specimens have a pivotal role in the diagnosis, prognosis and management of patients with renal cell carcinoma (RCC).

METHODS

A non-systematic literature search was performed, updated to January 2018, to identify key standards and controversies in the pathological classification, grading and staging of RCC.

RESULTS

Although most RCCs exhibit characteristic morphology that enables easy categorisation, RCCs show considerable morphological heterogeneity and it is not uncommon for there to be difficulty in assigning a tumour type, especially with rarer tumour subtypes. The differentiation between benign and malignant oncocytic tumours remains a particular challenge. The development of additional immunohistochemical and molecular tests is needed to facilitate tumour typing, because of the prognostic and therapeutic implications, and to enable more reliable identification of poorly differentiated metastatic tumours as being of renal origin. Any new tests need to be applicable to small biopsy samples, to overcome the heterogeneity of renal tumours. There is also a need to facilitate identification of tumour types that have genetic implications, to allow referral and management at specialist centres. Digital pathology has a potential role in such referral practice.

CONCLUSION

Much has been done to standardise pathological assessment of renal cell carcinomas in recent years, but there still remain areas of difficulty in classification and grading of these heterogeneous tumours.

Update on the biology and management of renal cell carcinoma

Renal cell cancer (RCC) (epithelial carcinoma of the kidney) represents 2%-4% of newly diagnosed adult tumors. Over the past 2 decades, RCC has been better characterized clinically and molecularly. It is a heterogeneous disease, with multiple subtypes, each with characteristic histology, genetics, molecular profiles, and biologic behavior. Tremendous heterogeneity has been identified with many distinct subtypes characterized. There are clinical questions to be addressed at every stage of this disease, and new targets being identified for therapeutic development. The unique characteristics of the clinical presentations of RCC have led to both questions and opportunities for improvement in management. Advances in targeted drug development and understanding of immunologic control of RCC are leading to a number of new clinical trials and regimens for advanced disease, with the goal of achieving long-term disease-free survival, as has been achieved in a proportion of such patients historically. RCC management is a promising area of ongoing clinical investigation.

Declining incidence of benign lesions among small renal masses treated with surgery: Effect of diagnostic tests for characterization

PURPOSE

We evaluated the changes in the incidence of benign lesions in surgically removed small renal masses (SRMs) and the effect of diagnostic tests for characterizing SRMs.

METHODS

We included 2,707 patients receiving surgery for SRMs (<4cm). Trends in the incidence of benign histology were evaluated according to the surgery year (period 1: 2001-2005, 2: 2006-2010, and 3: 2011-2015). Multivariable logistic regression analysis was performed to identify factors associated with benign lesions. Additionally, the number of surgeries prevented due to benign histological findings on renal mass biopsies (RMB) done on 206 patients with SRM during study period was evaluated.

RESULTS

Benign histology was identified in 192 (7.1%) patients. Incidence of benign histology was 9.7%, 7.0%, and 6.3% for period 1, 2 and 3, respectively. The uses of multiphase computed tomography and magnetic resonance imaging were more common in periods 2 and 3 than in period 1 (P<0.001). The use of RMB in period 3 was higher than in periods 1 and 2 (0.8 vs. 0.9 vs. 9.0%, P<0.001). In multivariable analysis, older age, male sex, larger tumor size, and recent surgery year (period 3 vs. 1, odds ratio = 0.62, P = 0.028) were independently associated with decreased odds of benign lesions. The number of prevented surgeries by performing RMB was 0, 10, and 39 in periods 1, 2, and 3, respectively.

CONCLUSIONS

Incidence of benign histology after surgery for SRMs declined during recent years, which might be associated with the recent increased use of RMB.

Outcomes of ultrasound guided renal mass biopsies

PURPOSE

The purpose of this study was to evaluate the rate of nondiagnostic ultrasound-guided renal mass biopsies (RMBs) at our institution and to determine what patient, procedural, and focal renal mass (FRM) factors were associated with nondiagnostic ultrasound-guided RMBs.

METHODS

Eighty-two ultrasound-guided renal mass biopsies performed between January 2014 and October 2016 were included in our study. Biopsy outcomes (diagnostic vs. nondiagnostic) and patient, procedural, and FRM characteristics were retrospectively reviewed and recorded. Univariate statistical analyses were performed to identify biopsy characteristics that were indicative of nondiagnostic biopsy.

RESULTS

Ultrasound-guided RMBs were diagnostic in 70 out of 82 cases (85%) and non-diagnostic in 12 cases (15%). Among the diagnostic biopsies, 54 (77%) were malignant cases, 94% of which were renal cell carcinoma (RCC). Of the 12 nondiagnostic cases, the final diagnosis was RCC in 4 cases and angiomyolipoma in one case; seven of the nondiagnostic cases were lost to follow-up. A weak association (p = 0.04) was found between the number of needle passes and the biopsy outcome. None of the remaining collected RMB characteristics showed a significant correlation with a diagnostic or nondiagnostic RMB. Six patients (7%) experienced complications.

CONCLUSION

Ultrasound-guided renal mass biopsy is a safe and effective method for the diagnosis of renal masses with a low rate of nondiagnostic outcomes. A nondiagnostic biopsy should not be treated as a surrogate for a diagnosis since a significant number of patients with nondiagnostic biopsies have subsequently been shown to have renal malignancies. Repeat biopsy should be considered in such cases.

CT-based radiomic model predicts high grade of clear cell renal cell carcinoma

PURPOSE

To compare the predictive models that can incorporate a set of CT image features for preoperatively differentiating the high grade (Fuhrman III-IV) from low grade (Fuhrman I-II) clear cell renal cell carcinoma (ccRCC).

MATERIAL AND METHODS

One hundred and fourteen patients with ccRCC treated with a partial or radical nephrectomy were enrolled in the training cohort. The six non-texture features, including Pseudocapsule, Round mass, maximal tumor diameter (Diameter_max), intratumoral artery (Artery_tumor), enhancement value of the tumor (TEV) and relative TEV (rTEV), were assessed for each tumor. The texture features were extracted from the CT images of the section with the largest area of renal mass at both corticomedullary and nephrographic phases. The least absolute shrinkage and selection operator (LASSO) was used to screen the most valuable texture features to calculate a texture score (Texture-score) for each patient. A logistic regression model was used in the training cohort to discriminate the high from low grade ccRCC at nephrectomy. The predictors would include all non-texture features in Model 1, all non-texture features and Texture-score in Model 2, and Texture-score in Model 3. The performance of the predictive models were tested and compared in an independent validation cohort composed of 92 cases with ccRCC.

RESULTS

Inter-rater agreement was good for each non-texture feature and Texture-score (the concordance correlation coefficient or Kappa coefficient > 0.70). The Texture-score was calculated via a linear combination of the 4 selected texture features. The three models shown good discrimination of the high from low grade ccRCC in the training cohort and the area under receiver operating characteristic curve (AUC) was 0.826 in Mode 1, 0.878 in Model 2 and 0.843 in Model 3, and a significant different AUC was found between Model 1 and Model 2. Application of the predictive models in the validation cohort still gave a discrimination (AUC > 0.670), and the Texture-score based models with or without the non-texture features (Model 2 and 3) showed a better discrimination of the high from low grade ccRCC (P < 0.05).

CONCLUSION

This study presented the Texture-score based models can facilitate the preoperative discrimination of the high from low grade ccRCC.

Morphologic analysis with computed tomography may help differentiate fat-poor angiomyolipoma from renal cell carcinoma: a retrospective study with 602 patients

PURPOSE

To assess whether morphologic analysis using computed tomography (CT) could differentiate between fat-poor angiomyolipoma (fpAML) and renal cell carcinoma (RCC).

METHODS

A total of 602 patients with a histologically confirmed fpAML (n = 49) or RCC (n = 553) were evaluated. All renal lesions were less than 4 cm in size and had no gross fat on contrast-enhanced CT. For morphologic analysis, overflowing beer sign and angular interface were evaluated. Overflowing beer sign was defined as contact length between bulging-out portion of a mass and the adjacent renal capsule of 3 mm or greater. Angular interface was defined as the angle of parenchymal portion of a mass of 90° or less. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were assessed. Multivariate analysis was conducted to determine which variable is predictive of fpAML.

RESULTS

Sensitivity, specificity, PPV, NPV, and accuracy were 61.2% (30/49), 97.1% (537/553), 65.2% (30/46), 96.6% (537/556), and 94.2% (567/602) with overflowing beer sign, while they were 55.1% (27/49), 81.9% (453/553), 21.3% (27/127), 95.4% (453/475), and 79.7% (480/602) with angular interface for fpAML, respectively. Both CT variables were predictive of fpAML (overflowing beer sign, odds ratio = 132.881, p < 0.001; angular interface, odds ratio = 5.766, p = 0.010). The multivariate model with CT variables showed good performance for predicting fpAML (AUC, 0.871 with angular interface, 0.943 with overflowing beer sign, and 0.949 with both).

CONCLUSION

Morphologic analysis with contrast-enhanced CT may be useful for differentiating fpAML from RCC. Overflowing beer sign has the potential as an imaging biomarker for fpAML.

Image-guided biopsy of small (≤4 cm) renal masses: the effect of size and anatomical location on biopsy success rate and complications

OBJECTIVE

To study the influence of tumour diameter and anatomy on the success and complication rates of small renal mass (SRM, ≤4 cm) core biopsy.

METHODS

Retrospective analysis of SRMs that underwent ultrasound or CT-guided biopsy. Diagnostic and complication rates were compared according to tumour size (subcategorised as axial diameter ≤2 cm, >2 to- ≤3 cm, >3-≤4 cm) and anatomical disposition (exophytic/endophytic, centrality, polar location and anterior/posterior).

RESULTS

94 patients (54 male; age range 21.8-84.3 years) with 95 SRMs underwent biopsy. The first biopsy was diagnostic in 81/95 (85.3%). Seven patients underwent repeat biopsy (6/7 diagnostic), to give an overall diagnostic rate of 91.5%. The primary diagnostic rates in the ≤2, >2-≤3 , >3-≤4 cm groups were 21/25 (84%); 38/44 (86.4%) and 22/26 (84.6%) respectively and were similar (p = 1.00). Anterior and upper pole SRMs were more likely to fail initial biopsy (odds ratio 13.8, p < 0.01; and odds ratio 4.35, p = 0.04) respectively, but other anatomical factors were not relevant. Complications occurred in 14% (all conservatively managed perinephric haematomas; Clavien-Dindo Grade 1) and size or location were not relevant.

CONCLUSION

Image-guided biopsy of SRMs has a high diagnostic rate irrespective of tumour size. Anterior and upper pole location had lower diagnostic rates. Biopsy should be considered for all patients with SRMs, if the result will impact on management and we list specific scenarios where an SRM biopsy may be helpful. Advances in knowledge: SRM size does not affect the likelihood of a diagnostic biopsy.

Solid Small Renal Mass Without Gross Fat: CT Criteria for Achieving Excellent Positive Predictive Value for Renal Cell Carcinoma

OBJECTIVE

The purpose of this study was to evaluate CT criteria for achieving high positive predictive value (PPV) for renal cell carcinoma (RCC) in patients with solid small renal masses (SRMs) less than 4 cm without macroscopic fat.

MATERIALS AND METHODS

One hundred fifty consecutive patients with a solid SRM without macroscopic fat (mean size ± SD, 2.5 ± 0.8 cm) who underwent CT including unenhanced, corticomedullary (CMP), and nephrographic phases (NP) were evaluated. Pathologically proven solid SRMs without macroscopic fat were classified into RCC (n = 131) and not RCC (n = 19). A "persistent low" sign was defined as a focal area or areas of low attenuation seen at the same location within the lesion on both CMP and NP imaging. Calcification, shape, and lesion attenuation on unenhanced CT were analyzed by two independent readers.

RESULTS

PPV of CT criteria (calcification [criterion 1] or spherical shape, lower or equal attenuation, and persistent low sign [criterion 2]) for RCC was 98.3% (58/59) for reader 1 and 100% (53/53) for reader 2. Weighted kappa of interreader agreement was 1.000 for calcification, 0.966 of lower or equal attenuation, 0.834 for spherical shape, 0.823 for persistent low sign, and 0.829 for CT criteria.

CONCLUSION

Interpretation of CT allowed reproducible and excellent PPV for RCC. Current CT criteria may effectively shorten the management process for solid SRMs without macroscopic fat by reducing unnecessary biopsy for a substantial number of RCCs showing typical CT findings.

Differential diagnosis of the small renal masses: role of the apparent diffusion coefficient of the diffusion-weighted MRI

INTRODUCTION

Renal cell carcinoma (RCC) accounts for approximately 3% of adult malignancies and more than 90% of neoplasms arising from the kidney. Uninformative percutaneous kidney biopsies vary from 10 to 23%. As a result, 7.5-33.6% of partial nephrectomies in patients with small renal masses (SRM) are performed on benign renal tumors. The aim of this study was to assess the feasibility of the apparent diffusion coefficient (ADC) of the diffusion-weighted imaging (DWI) of MRI, as RCC imaging biomarker for differentiation of SRM.

METHOD

Adult patients (n = 158) with 170 SRM were enrolled into this study. The control group were healthy volunteers with normal clinical and radiologic findings (n = 15). All participants underwent MRI with DWI sequence included.

RESULTS

Mean ADC values of solid RCC (1.65 ± 0.38 × 10^-3 mm²/s) were lower than healthy renal parenchyma (2.47 ± 0.12 × 10^-3 mm²/s, p < 0.05). There was no difference between mean ADC values of ccRCC, pRCC and chRCC (1.82 ± 0.22 × 10^-3 vs 1.61 ± 0.07 × 10^-3 vs 1.46 ± 0.09 × 10^-3 mm²/s, respectively, p = ns). An inverse relationship between mean ADC values and Fuhrman grade of nuclear atypia of solid ccRCCs was observed: grade I-1.92 ± 0.11 × 10^-3 mm²/s, grade II-1.84 ± 0.14 × 10^-3 mm²/s, grade III-1.79 ± 0.10 × 10^-3 mm²/s, grade IV-1.72 ± 0.06 × 10^-3 mm²/s. This was significant (p < 0.05) only between tumors of I and IV grades. Significant difference (p < 0.05) between mean ADC values of solid RCCs, benign renal tumors and renal cysts was observed (1.65 ± 0.38 × 10^-3 vs 2.23 ± 0.18 × 10^-3 vs 3.15 ± 0.51 × 10^-3 mm²/s, respectively). In addition, there was a significant difference (p < 0.05) in mean ADC values between benign cysts and cystic RCC (3.36 ± 0.35 × 10^-3 vs 2.83 ± 0.21 × 10^-3 mm²/s, respectively).

CONCLUSION

ADC maps with b values of 0 and 800 s/mm² can be used as an imaging biomarker, to differentiate benign SRM from malignant SRM. Using ADC value threshold of 1.75 × 10^-3 mm²/s allows to differentiate solid RCC from solid benign kidney tumors with 91% sensitivity and 89% specificity; ADC value threshold of 2.96 × 10^-3 mm²/s distinguishes cystic RCC from benign renal cysts with 90% sensitivity and 88% specificity. However, the possibility of differentiation between ccRCC histologic subtypes and grades, utilizing ADC values, is limited.

Use of 99mTc-sestamibi Single-photon Emission Computed Tomography / X-ray Computed Tomography in the Diagnosis of Hybrid Oncocytic / Chromophobe Tumor in a Pediatric Patient

The differential diagnosis of solid renal neoplasms in adolescence includes aggressive malignancy and indolent oncocytic tumors, which are typically indistinguishable using conventional imaging. We report the use of ^99mTc-sestamibi single-photon emission computed tomography / x-ray computed tomography (SPECT/CT) in characterizing enhancing renal neoplasms in a pediatric patient. Genetic testing suggested a hereditary syndrome associated with aggressive malignancy, whereas renal mass biopsy suggested an oncocytic tumor. ^99mTc-sestamibi SPECT/CT indicated probable oncocytomas or hybrid oncocytic / chomophobe tumors. Enucleative resection was performed with final pathology demonstrating hybrid oncocytic / chomophobe tumors. This case highlights the potential utility of ^99mTc-sestamibi SPECT/CT in characterizing indeterminate enhancing renal neoplasm in pediatric patients.

Active Surveillance in Small Renal Masses in the Elderly: A Literature Review

CONTEXT

Small renal masses have become increasingly common due to widespread imaging; however, optimal management of these lesions in the elderly can be complex due to the competing risks of intervention, natural history of disease, patient comorbidities, and expectations. In the properly selected elderly patient, active surveillance remains an accepted and attractive treatment approach.

OBJECTIVE

We completed a literature review of small renal masses (enhancing, <4cm, T1aN0M0 disease) in the elderly, aged ≥70 yr, aimed at identifying the utility of active surveillance in this population. The primary outcomes were conversion to active treatment while on active surveillance and cancer-specific mortality. Secondary outcomes included predictors of treatment, type of treatment performed (partial nephrectomy, radical nephrectomy, and ablation), progression to metastases, all-cause mortality, tumor growth rate, and demographic data including age and Charlson Comorbidity Index.

EVIDENCE ACQUISITION

A comprehensive search of electronic databases (e.g., MEDLINE, EMBASE, SCOPUS, Web of Science, and the Cochrane Library) using search terms "small renal mass" OR "SRM", AND "elderly," "senior," "aging," "geriatric," OR "octogenarian" was completed. All randomized controlled trials, nonrandomized comparison studies, and case series were included and screened by the reviewers. All comparison studies included in the systematic review were assessed for methodological quality using the Cochrane Risk of Bias tools.

EVIDENCE SYNTHESIS

Seventeen primary studies including 36495 patients met the inclusion criteria for the systematic review. All studies were retrospective institutional chart or the Surveillance, Epidemiology, and End Results database reviews. There was a low (4-26%) rate of conversion to active treatment for active surveillance in the identified studies over a follow-up interval of up to 91.5 mo. Overall mortality was substantial in this elderly cohort, with 15-51% of patients being deceased over the course of study follow-up; however, there was minimal cancer-specific mortality due to patients succumbing to alternative comorbid disease. In the future, patient comorbidity and biological age versus the natural history of the individualized tumor biology may play an increasing role in the discussion regarding treatment options and consideration of active surveillance.

CONCLUSIONS

Active surveillance is an effective management strategy in the elderly population. Few patients required the conversion to active treatment and there was low cancer-specific mortality. The majority of patients who expired over the course of the identified studies succumbed to alternative disease. The goal of treatment strategies should include weighing patient-specific prognosis relative to their competing health risks and treatment goals against the natural history of disease and risks of intervention.

PATIENT SUMMARY

In this review article, the authors examined the utility of active surveillance in the setting of a small localized renal mass in the elderly population. Despite being on surveillance, we found that cancer-specific outcomes were excellent, and overall mortality was often a result of comorbid disease. However, there is significant heterogeneity among elderly patients, and treatment approaches should be focused around patient-centered goals and prognosis.

Management of the small renal mass

The increasing use of cross-sectional imaging has led to an increase in the diagnosis of incidental small renal masses (SRMs). About 20% of such masses are benign, while a significant proportion of malignant SRMs demonstrate slow growth kinetics and non-aggressive histologic features. Given these characteristics, lesions that were traditionally treated surgically are increasingly managed with less aggressive approaches. Further contributing to the evolving management paradigm is accumulating evidence supporting the safety of active surveillance and the efficacy of percutaneous renal mass biopsy in guiding management decisions. This review first discusses the epidemiology and diagnostic work-up of SRMs. The available management options are then examined, with emphasis placed on the clinical factors considered in selecting an appropriate approach. The existing evidence and long-term outcomes of each strategy are discussed. Finally, an overview of the current paradigm for the management of a patient with a SRM is provided. The goal is to provide physicians with the necessary understanding to appropriately manage this increasingly common condition.

Diagnostic Needle Biopsies in Renal Masses: Patient and Physician Perspectives

BACKGROUND

The utility of renal mass biopsies (RMB) in the diagnosis of kidney tumors remains debatable.

OBJECTIVE

To assess patient and urologist preferences regarding the utilization of RMB.

DESIGN, SETTING, AND PARTICIPANTS

Seventy-three patients diagnosed with renal tumors and 59 board-certified urologists were asked to participate in an interview-based study.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Using the standard gamble method we determined the minimal accepted accuracy at which RMB would be favored as part of the diagnostic process. Clinical and demographic data with potential to affect participants' preferences were analyzed.

RESULTS AND LIMITATIONS

At the time of the study interview, 56 patients (77%) were referred for kidney surgery and 17 (23%) opted for surveillance. Overall, 59% of the patients accepted some level of inaccuracy (1-20%), whereas 27% refuted a biopsy. Anxiety associated with the possibility of missing cancer was the primary determinant (82%) for declining RMB among patients referred for surgery, while fear of complications was the primary reason (58%) among those undergoing surveillance. Having an academic degree was associated with a lower accuracy threshold (p=0.03). Of the 59 participating urologists, 39% were reluctant to recommend RMB, primarily because of its inexorable nondiagnostic rate.

CONCLUSIONS

Most patients and urologists would favor RMB to facilitate their definitive treatment decision. Diagnostic accuracy of 95% was acceptable by the majority of study participants. The utility of RMB as part of the diagnostic algorithm for renal tumors should be discussed with patients, emphasizing its potential benefits and limitations.

PATIENT SUMMARY

Although needle biopsy seems to be an effective tool to differentiate benign from malignant kidney lesions, it is not commonly used. Our study shows that most patients would opt for a biopsy before definitive treatment decision despite its imperfect accuracy. Hence, the option of undergoing renal biopsy should be discussed with all patients diagnosed with small renal tumors.

Update on Renal Mass Biopsy

Renal masses are diagnosed with an increasing frequency. However, a significant proportion of these masses are benign, and the majority of malignant tumors are biologically indolent. Furthermore, renal tumors are often harbored by the elderly and comorbid patients. As such, matching of renal tumor biology to appropriate treatment intensity is an urgent clinical need. Renal mass biopsy is currently a very useful clinical tool that can assist with critical clinical decision-making in patients with renal mass. Yet, renal mass biopsy is associated with limitations and, as such, may not be appropriate for all patients.

Surgical histopathology for suspected oncocytoma on renal mass biopsy: a systematic review and meta-analysis

To estimate the proportion of oncocytic renal neoplasms diagnosed on renal mass biopsy (RMB) confirmed on surgical pathology, a systematic review of MEDLINE, Embase, and the Cochrane databases (1997 to 1 July 2016) was conducted quantifying all cases of reported oncocytic renal neoplasms on RMB suggestive of an oncocytoma. In addition, institutional data was assessed to identify additional cases. Concordance with surgical histopathology (positive predictive value [PPV]) was evaluated for patients undergoing surgery by performing a meta-analysis. In all, 10 RMB series, including institutional data, were included in the meta-analysis with 205 RMBs identifying oncocytic renal neoplasms and 46 (22.4%) proceeding to surgery. One additional study identified two neoplasms not captured by the primary RMB series for a total of 48 unique lesions included in the analysis. Surgical pathology showed oncocytoma (64.6%), chromophobe renal cell carcinoma (RCC; 12.5%), other RCC (12.5%), hybrid oncocytic/chromophobe tumour (6.3%), and other benign lesions (4.2%). PPV of oncocytoma on RMB was 67% (95% confidence interval 34-94%) with significant heterogeneity between studies (I² = 71.8%, P < 0.01). Risk of bias was judged to be low for four of the 10 series. Confidently diagnosing a localised renal mass as a benign lesion, such as an oncocytoma, has implications for the ultimate management strategy a patient will undergo. RMB was found to be unreliable in confidently diagnosing a localised renal mass as an oncocytoma, with one in four found to be RCC on surgical pathology. Patients and physicians should be aware of the uncertainty in diagnosis when considering management strategies.

Cost Comparisons Between Different Techniques of Percutaneous Renal Biopsy for Small Renal Masses

PURPOSE

To compare the costs associated with ultrasound (US)-guided hospital-based (UGHB), CT-guided hospital-based (CTG), and US-guided office-based (UGOB) percutaneous renal biopsy (PRB) for small renal masses (SRMs).

METHODS

We retrospectively analyzed patient demographics, tumor characteristics, R.E.N.A.L. nephrometry scores, and cost data of patients undergoing PRB for SRM at our institution from May 2012 to September 2015. Cost data, including facility costs, professional fees, and pathology, were obtained from the departments of urology, radiology, and pathology.

RESULTS

A total of 78 patients were included in our analysis: 19, 31, and 28 UGHB, CTG, and UGOB, respectively. There was no difference in age, gender distribution, or tumor size among the three groups (p-values 0.131, 0.241, and 0.603, respectively). UGOB tumors had lower R.E.N.A.L. nephrometry scores (p=0.008). There were no differences in nondiagnostic rates between the UGHB, CTG, and UGOB groups [4 (21%), 5 (16%), and 6 (21%)] (p=0.852). There were no differences in final tumor treatment strategies utilized among the UGHB, CTG, and UGOB groups (p=0.447). There were 0, 2 (6%), and 0 complications in the UGHB, CTG, and UGOB biopsy groups. Total facility costs were $3449, $3280, and $1056 for UGHB, CTG, and UGOB PRB, respectively (p<0.0001). There was no difference between the urologist's and radiologist's professional fees (p=0.066). Total costs, including facility costs, pathology fees, and professional fees, were $4598, $4470, and $2129 for UGHB, CTG, and UGOB renal biopsy, respectively (p<0.0001).

CONCLUSION

For select patients with less anatomically complex, exophytic, and posteriorly located tumors, UGOB PRB provides equivalent diagnostic and complication rates while being significantly more cost-effective than either UGHB or CTG renal biopsy.

Clear cell renal cell tumors: Not all that is "clear" is cancer

Continued improvement of our understanding of the clinical, histologic, and genetic features of renal cell tumors has progressively evolved renal tumor classification, revealing an expanding array of distinct tumor types with different implications for prognosis, patient counseling, and treatment. Although clear cell renal cell carcinoma is unequivocally the most common adult renal tumor, there is growing evidence that some "clear cell" renal neoplasms, such as exemplified by multilocular cystic clear cell renal neoplasm of low malignant potential (formerly multilocular cystic renal cell carcinoma), do not have the same potential for insidious progression and metastasis, warranting reclassification as low malignant potential tumors or benign neoplasms. Still other novel tumor types such as clear cell papillary renal cell carcinoma have been more recently recognized, which similarly have shown a conspicuous absence of aggressive behavior to date, suggesting that these too may be recategorized as noncancerous or may be premalignant neoplasms. This importance for prognosis is increasingly significant in the modern era, in which renal masses are increasingly found incidentally by imaging techniques at a small tumor size, raising consideration for less aggressive management options guided by renal mass biopsy diagnosis, including imaging surveillance, tumor ablation, or partial nephrectomy.