Fine-needle percutaneous biopsy of renal masses with helical CT guidance

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.

[Renal Biopsy]

The extent of renal biopsy indication is being widened because of the increasing incidence of incidental renal masses; the increasing treatment options for renal cell carcinoma, including ablation therapy and novel targeted treatment; and the increasing incidence of kidney transplantation. However, percutaneous renal biopsy is technically difficult, particularly for beginners, because the skin-to-organ distance is relatively longer than those associated with other organs. In the present review, we will discuss the indications, technical considerations, efficacy, and complications of renal biopsy. Furthermore, we share practical tips of renal biopsy through many examples to help radiologists perform renal biopsy safely and effectively in various situations.

Utility of cytopathologic diagnosis of adult solid renal lesions: An academic Institution's 10-year experience

BACKGROUND

Fine needle aspiration (FNA) and/or needle core biopsy (NCB) are increasingly used for managing patients with renal lesions, especially small renal masses (SRMs). One of the treatment options for SMRs is active surveillance. Hence, accurate diagnosis of renal lesions is critical for treatment planning. The aim of this study is to investigate the utility of FNA and/or NCB in the diagnosis of adult renal lesions at our institute.

MATERIALS AND METHODS

Laboratory information system was queried over a period of 10 years (2011-2020) to identify cases of FNA and/or NCB with touch preparation (TP) of adult renal masses. Patient demographics, cytopathologic diagnoses, ancillary tests and follow-up surgical resection data were reviewed and correlated.

RESULTS

A total 138 cases from 138 patients (male = 80, female = 58) were identified. Sixty-one (44.20%) cases had FNA and NCB, 48 (34.78%) had NCB only and 29 (21.01%) had FNA only. 118 (85.50%) cases had definitive diagnoses and 13 (9.42%) had indeterminant diagnoses and seven cases were non-diagnostic (5.07%). Most common benign and malignant diagnoses were oncocytoma and clear cell renal cell carcinoma (CCRCC). 41/138 (29.71%) cases had follow-up resection. There were no false positive or false negative cases. Subtyping was feasible in majority cases with only 3/138 (2.17%) misclassified cases.

CONCLUSIONS

Majority of renal masses (85.50%) had definitive cytology diagnoses. Only three had misclassification. FNA and/or NCB are useful methods in diagnosing and subclassifying adult renal masses and showed high accuracy (91.89%) when compared to surgical resections.

Efficacy and Safety of CT-Guided Kidney Biopsy for the Diagnosis of Glomerular Diseases in Complicated Patients

INTRODUCTION

Kidney biopsy is the cornerstone for the diagnosis of glomerular diseases and to guide treatment. Percutaneous ultrasound-guided kidney biopsy is currently the gold standard to obtain cortical specimens. However, in cases where ultrasound-guided kidney biopsy is not deemed safe (obese patients, deep kidneys, or kidneys with a complicated anatomy), CT-guided kidney biopsy could be a convenient alternative to obtain renal tissue samples. The aim of this study was to describe the diagnostic yield and complications of CT-guided kidney biopsies in patients with glomerular diseases that were previously discarded for ultrasound-guided kidney biopsy.

MATERIAL AND METHODS

We performed a retrospective, single-center, observational study including patients who underwent CT-guided native kidney biopsies in our center after being contraindicated for ultrasound-guided biopsy. Patients' records were reviewed retrieving baseline characteristics and pre-biopsy clinical, laboratory parameters and concomitant medication. The biopsy needle gauge, site of puncture, and number of needle passes were recorded. The diagnostic yield was evaluated by the number of glomeruli obtained, the rate of specimens that were adequate to reach diagnosis, and the number of biopsies that had to be repeated. Complications were defined as minor (hypotension, hematoma) and major (arteriovenous fistulae, major bleeding requiring embolization, or nephrectomy). The diagnostic yield and complications were compared to ultrasound-guided native kidney biopsies performed during the same period.

RESULTS

56 CT-guided native kidney biopsies were performed during the study period. The number of glomeruli obtained per patient was 11.5 ± 6.3, which was inferior to that obtained from ultrasound-guided biopsies (14.08 ± 8.47, p < 0.05). However, the rate of specimens that were adequate to reach a diagnosis was similar (92.9% vs. 90.8%, p = 0.437). The number of needle passes was higher in CT-guided kidney biopsies (2.0 ± 0.7 vs. 1.7 ± 0.5, p < 0.05), as well as the incidence of post-biopsy perirenal asymptomatic hematomas (66.1% vs. 24.5%, p < 0.01). There were no significant differences in other post-biopsy minor complications (1.8% vs. 2.5%, p = 0.621). There were no major complications after CT-guided kidney biopsies.

CONCLUSIONS

CT-guided percutaneous kidney biopsy is a valid alternative for the diagnosis of glomerular diseases in patients with special characteristics such as obesity or deep kidneys that contraindicate ultrasound-guided biopsy. In this population, CT-guided kidney biopsies are safe and provide a high diagnostic yield, reaching a diagnosis in >90% of patients that had been previously discarded for ultrasound-guided biopsy.

[Evolution of followed renal oncocytomas]

INTRODUCTION

Oncocytomas are primitive kidney tumours, considered benign but their evolution is not fully established. The local progression is generally admitted but few data explain what makes a oncocytoma to grow more or less quickly. The objective of our study is to analyse the evolution of followed renal oncocytomas after histologic confirmation and to identify factors that can influence their growth.

MATERIAL AND METHODS

This is a retrospective study in two centers (North Hospital and Hospital of the Conception of Marseille). All patients with renal oncocytoma diagnosed with percutaneous biopsy from September 2010 to April 2016 and followed for more than one year were included. Epidemiological, histological, and morphological data were collected at diagnosis, during follow-up and in case of strategy change (intervention). Statistical analysis of factors influencing oncocytomes growth was based on the Pearson correlation test.

RESULTS

Fifty-three patients were included. The median age for diagnosis was 65 years [39-85]. The sex ratio H/F was 6/5. The median follow-up was 34 months [12-180]. The average diagnosis size was 29 mm [12-90]. Thirteen patients (25%) were treated secondarily, including 70% by conservative treatment. The average growth was 0.25 (±0.23) cm/yr. The patients treated were younger and had a higher growth rate than the untreated (0.48±0.23cm/yr versus 0.18±0.18cm/yr, P<0,001). According to Pearson's analysis, there was a positive linear relationship (R=0.27, P=0.047) between velocity and initial size and a negative linear relationship (ρ=-0.44, P<0.001) between velocity and age at diagnosis. So tumor growth was faster if the patients were young and the tumor voluminous at diagnosis.

DISCUSSION

Rapid growth often leads to a cessation of surveillance in favour of an intervention strategy. For young patients, conservative treatment (partiel nephrectomy or ablative treatment) in the medium term is likely to be preferred, but for elderly patients or with important comorbidities follow-up is an alternative to an invasive attitude.

LEVEL OF EVIDENCE

3.

Unenhanced CT Texture Analysis of Clear Cell Renal Cell Carcinomas: A Machine Learning-Based Study for Predicting Histopathologic Nuclear Grade

OBJECTIVE. The purpose of this study is to investigate the predictive performance of machine learning (ML)-based unenhanced CT texture analysis in distinguishing low (grades I and II) and high (grades III and IV) nuclear grade clear cell renal cell carcinomas (RCCs). MATERIALS AND METHODS. For this retrospective study, 81 patients with clear cell RCC (56 high and 25 low nuclear grade) were included from a public database. Using 2D manual segmentation, 744 texture features were extracted from unenhanced CT images. Dimension reduction was done in three consecutive steps: reproducibility analysis by two radiologists, collinearity analysis, and feature selection. Models were created using artificial neural network (ANN) and binary logistic regression, with and without synthetic minority oversampling technique (SMOTE), and were validated using 10-fold cross-validation. The reference standard was histopathologic nuclear grade (low vs high). RESULTS. Dimension reduction steps yielded five texture features for the ANN and six for the logistic regression algorithm. None of clinical variables was selected. ANN alone and ANN with SMOTE correctly classified 81.5% and 70.5%, respectively, of clear cell RCCs, with AUC values of 0.714 and 0.702, respectively. The logistic regression algorithm alone and with SMOTE correctly classified 75.3% and 62.5%, respectively, of the tumors, with AUC values of 0.656 and 0.666, respectively. The ANN performed better than the logistic regression (p < 0.05). No statistically significant difference was present between the model performances created with and without SMOTE (p > 0.05). CONCLUSION. ML-based unenhanced CT texture analysis using ANN can be a promising noninvasive method in predicting the nuclear grade of clear cell RCCs.

Evaluation of diagnostic accuracy and a practical algorithmic approach for the diagnosis of renal masses by FNA

BACKGROUND

The classification of renal neoplasms is essential for oncologic risk stratification and clinical management, and an accurate pretreatment pathologic diagnosis can provide useful guidance for active surveillance, minimally invasive ablative therapy, or surgical resection and can reduce the incidence of overtreatment. Previous studies evaluating the diagnostic accuracy of fine-needle aspiration (FNA) and core-needle biopsy (CNB) for renal masses are limited and show variable results.

METHODS

Two hundred forty-seven renal FNA cases with or without concurrent CNB performed and/or reviewed at the Stanford University School of Medicine over the course of 20 years were identified. Cytohistopathologic correlation was performed for 77 cases with subsequent resection specimens. All available case materials were reviewed, and select cases were worked up further and reclassified as necessary.

RESULTS

Cytohistopathologic correlation showed 96% diagnostic specificity and 83% sensitivity for renal FNA with or without concurrent CNB. Discordant cases were mostly attributed to sampling errors or suboptimal specimens (79%) and also included 2 non-renal cell carcinoma entities (1 case of angiomyolipoma and 1 case of a benign peripheral nerve sheath tumor) and 1 case involving misclassification of the renal cell carcinoma subtype.

CONCLUSIONS

There is considerable value in FNA/CNB for the initial diagnosis of renal masses because of the high diagnostic specificity and sensitivity. Sensitivity is predominantly dependent on sufficient sampling, and additional potential diagnostic pitfalls include nonepithelial and rare entities. Judicious use of ancillary techniques is encouraged, especially when one is presented with a limited specimen, and this article presents a practical algorithmic approach to the diagnosis of renal masses using salient morphologic features and results from ancillary studies. Fine-needle aspiration is an accurate method for the diagnosis of renal masses. A practical diagnostic algorithm, based on salient morphologic and ancillary findings, is presented.

Meta-analysis of diffusion-weighted imaging in the differential diagnosis of renal lesions

PURPOSE

To assess the diagnostic value of diffusion-weighted imaging (DWI) in distinguishing between renal malignant and benign lesions.

MATERIALS AND METHODS

Electronic databases were systematically searched to identify original studies evaluating DWI findings on renal lesions from January 2000 through January 2018. Pooled weighted estimates of sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were calculated. A summary receiver operator characteristic (sROC) curve was constructed to calculate the area under the sROC curve (AUC). Publication bias was assessed by using Deeks' asymmetry test.

RESULTS

A total of 15 studies including 1386 renal lesions were eligible in the meta-analysis. The pooled sensitivity and specificity with a corresponding 95% confidence interval (CI) were 0.83 (95% CI: 0.80-0.86) and 0.74 (95% CI: 0.71-0.78), respectively. The PLR, NLR, and DOR were 3.21 (95% CI: 2.39-4.32), 0.24 (95% CI: 0.18-0.30), and 15.95 (95% CI: 11.19-22.71), respectively. The AUC was 0.87 (95% CI: 0.84-0.90). Significant heterogeneity was observed between the included studies. Reference standard, country, and gradient factor were identified as the most important variable sources. No evidence of notable publication bias was reported.

CONCLUSIONS

DWI is an informative MRI modality in discriminating benign and malignant lesions and exhibits moderately high diagnostic accuracy. However, it remains inconclusive and limited in the absence of an optimal b value and ADC cutoff value. High-quality prospective studies regarding DWI have yet to be conducted to explore optimal imaging parameters and diagnostic thresholds.

Image-Guided Renal Interventions

Image-guided renal biopsies have an increasing role in clinical practice. Renal mass and renal parenchymal biopsy indications, techniques, and other clinical considerations are reviewed in this article. Image-guided renal mass ablation shows significant promise and increasing clinical usefulness as more studies demonstrate its safety and efficacy. Renal mass ablation indications, techniques, and other considerations are also reviewed.

Prediction and diagnosis of renal cell carcinoma using nuclear magnetic resonance-based serum metabolomics and self-organizing maps

Diagnosis of renal cell carcinoma (RCC) at an early stage is challenging, but it provides the best chance for cure. We aimed to develop a predictive diagnostic method for early-stage RCC based on a biomarker cluster using nuclear magnetic resonance (NMR)-based serum metabolomics and self-organizing maps (SOMs). We trained and validated the SOM model using serum metabolome data from 104 participants, including healthy individuals and early-stage RCC patients. To assess the predictive capability of the model, we analyzed an independent cohort of 22 subjects. We then used our method to evaluate changes in the metabolic patterns of 23 RCC patients before and after nephrectomy. A biomarker cluster of 7 metabolites (alanine, creatine, choline, isoleucine, lactate, leucine, and valine) was identified for the early diagnosis of RCC. The trained SOM model using a biomarker cluster was able to classify 22 test subjects into the appropriate categories. Following nephrectomy, all RCC patients were classified as healthy, which was indicative of metabolic recovery. But using a diagnostic criterion of 0.80, only 3 of the 23 subjects could not be confidently assessed as metabolically recovered after nephrectomy. We successfully followed-up 17 RCC patients for 8 years post-nephrectomy. Eleven of these patients who diagnosed as metabolic recovery remained healthy after 8 years. Our data suggest that a SOM model using a biomarker cluster from serum metabolome can accurately predict early RCC diagnosis and can be used to evaluate postoperative metabolic recovery.

Core Needle Biopsy and Fine Needle Aspiration Alone or in Combination: Diagnostic Accuracy and Impact on Management of Renal Masses

PURPOSE

Fine needle aspiration with and without concurrent core needle biopsy is a minimally invasive method to diagnose and assist in management of renal masses. We assessed the pathological accuracy of fine needle aspiration compared to and associated with core needle biopsy and the impact on management.

MATERIALS AND METHODS

We performed a single institution, retrospective study of 342 cases from 2001 to 2015 with small and large renal masses (4 or less and greater than 4 cm, respectively). Diagnostic and concordance rates, and the impact on management were analyzed.

RESULTS

Adequacy rates for fine needle aspiration only, core needle biopsy only and fine needle aspiration plus core needle biopsy were 21%, 12% and 8% (aspiration vs aspiration plus biopsy p <0.026). In the aspiration plus biopsy group adding aspiration to biopsy and biopsy to aspiration reduced the inadequacy rate from 23% to 8% and from 27% to 8% for a total reduction rate of 15% and 19%, respectively, corresponding to 32 cases (9.3%). Rapid on-site examination contributed to a 22.5% improvement in fine needle aspiration adequacy rates. In this cohort 30% of aspiration only, 5% of biopsy only and 12% of aspiration plus biopsy could not be subtyped (aspiration vs biopsy p <0.0001, aspiration vs aspiration plus biopsy p <0.0127 and biopsy vs aspiration plus biopsy p = 0.06). The diagnostic concordance rate with surgical resection was 99%. Conversion of an inadequate specimen to an adequate one by a concurrent procedure impacted treatment in at least 29 of 32 patients. Limitations include the retrospective design and accuracy measurement based on surgical intervention.

CONCLUSIONS

Fine needle aspiration plus core needle biopsy vs at least fine needle aspiration alone may improve diagnostic yield when sampling renal masses but it has subtyping potential similar to that of core needle biopsy only.

Aorta-Lesion-Attenuation-Difference (ALAD) on contrast-enhanced CT: a potential imaging biomarker for differentiating malignant from benign oncocytic neoplasms

OBJECTIVE

To evaluate whether the Aorta-Lesion-Attenuation-Difference on contrast-enhanced CT can aid in the differentiation of malignant and benign oncocytic renal neoplasms.

MATERIALS AND METHODS

Two independent cohorts-an initial (biopsy) dataset and a validation (surgical) dataset-with oncocytomas and chromophobe renal cell carcinomas (chRCC) were included in this IRB-approved retrospective study. A region of interest was placed on the renal mass and abdominal aorta on the same CT image slice to calculate an Aorta-Lesion-Attenuation-Difference (ALAD). ROC curves were plotted for different enhancement phases, and diagnostic performance of ALAD for differentiating chRCC from oncocytomas was calculated.

RESULTS

Seventy-nine renal masses (56 oncocytomas, 23 chRCC) were analyzed in the initial (biopsy) dataset. Thirty-six renal masses (16 oncocytomas, 20 chRCC) were reviewed in the validation (surgical) cohort. ALAD showed a statistically significant difference between oncocytomas and chromophobes during the nephrographic phase (p < 0.001), early excretory phase (p < 0.001), and excretory phase (p = 0.029). The area under the ROC curve for the nephrographic phase was 1.00 (95% CI: 1.00-1.00) for the biopsy dataset and showed the narrowest confidence interval. At a threshold value of 25.5 HU, sensitivity was 100 (82.2%-100%) and specificity was 81.5 (61.9%-93.7%). When tested on the validation dataset on measurements made by an independent reader, the AUROC was 0.93 (95% CI: 0.84-1.00) with a sensitivity of 100 (80.0%-100%) and a specificity of 87.5 (60.4%-97.8%).

CONCLUSIONS

Nephrographic phase ALAD has potential to differentiate benign and malignant oncocytic renal neoplasms on contrast-enhanced CT if histologic evaluation on biopsy is indeterminate.

Percutaneous biopsy of the renal mass: FNA or core needle biopsy?

BACKGROUND

In recent years, there have been increasing indications for percutaneous renal biopsy. Fine-needle aspiration (FNA), with or without core needle biopsy (CB), has been used increasingly in the management of renal tumors at the study institution.

METHODS

A computerized search of laboratory records was conducted to retrieve FNA cases of renal masses as well as the correlating CB and/or nephrectomy specimens. The cases spanned a period of 10 years (2006-2015). The diagnoses were classified into 5 categories: malignant, suspicious for malignancy, neoplastic, atypical, and negative/nondiagnostic. Based on the results of the nephrectomy specimens, the diagnostic rate, sensitivity, and diagnostic accuracy were calculated among 3 groups of specimens: FNA only, CB only, and combined FNA and CB.

RESULTS

A total of 247 cases of FNA with 123 correlating CB and 101 follow-up nephrectomy specimens were identified. The diagnostic rate, sensitivity, and diagnostic accuracy were 72%, 78%, and 96%, respectively, for FNA; 87%, 92%, and 94%, respectively, for CB; and 92%, 92%, and 94%, respectively, for the combined FNA and CB group. Renal cell carcinoma and its variants were the most common histologic diagnoses (112 of 174 cases; 64%). Significant diagnostic discrepancy was noted in one case: a malignant melanoma that was misdiagnosed as renal cell carcinoma in both the preoperative FNA specimen and in the CB specimen.

CONCLUSIONS

In the current study, both FNA and CB demonstrated excellent diagnostic accuracy (96% and 94%, respectively). The combination of FNA and CB was found to significantly improve the diagnostic rate when compared with either FNA alone (92% vs 72%; P<.05) or CB alone (92% vs 87%). Cancer Cytopathol 2017;125:407-15. © 2017 American Cancer Society.

Renal Tumor Biopsy Technique

Objective:

To review hot issues and future direction of renal tumor biopsy (RTB) technique.

Data Sources:

The literature concerning or including RTB technique in English was collected from PubMed published from 1990 to 2015.

Study Selection:

We included all the relevant articles on RTB technique in English, with no limitation of study design.

Results:

Computed tomography and ultrasound were usually used for guiding RTB with respective advantages. Core biopsy is more preferred over fine needle aspiration because of superior accuracy. A minimum of two good-quality cores for a single renal tumor is generally accepted. The use of coaxial guide is recommended. For biopsy location, sampling different regions including central and peripheral biopsies are recommended.

Conclusion:

In spite of some limitations, RTB technique is relatively mature to help optimize the treatment of renal tumors.

Diagnostic modalities

The incidental detection of small renal masses on imaging undertaken to evaluate unrelated symptoms or conditions is an increasingly common occurrence. Accurate imaging characterisation is fundamental to determining optimum patient management. The goals of imaging small renal masses include determining whether a lesion is solid or cystic, if there are signs of biological aggressiveness and whether the lesion is likely benign or malignant. The current imaging practices and the evidence supporting the use of different imaging modalities for the characterisation of small renal masses are discussed. CT remains the primary imaging modality and is able to classify most masses into surgical or non-surgical lesions. MRI and contrast enhanced ultrasound are most often employed to problem solve in lesions deemed indeterminate on contrast enhanced CT or for patients in which CECT is contraindicated. Percutaneous biopsy should be considered in lesions that remain indeterminate after initial imaging investigations. Given the central role of imaging in the management of small renal masses, all multidisciplinary team members involved in renal cancer care should have an understanding of the performance of the different imaging modalities.

PET-Based Percutaneous Needle Biopsy

PET can be used to guide percutaneous needle biopsy to the most metabolic lesion, improving diagnostic yield. PET biopsy guidance can be performed using visual or software coregistration, electromagnetic needle tracking, cone-beam computed tomography (CT), and intraprocedural PET/CT guidance. PET/CT-guided biopsies allow the sampling of lesions that may not be clearly visible on anatomic imaging, or of lesions that are morphologically normal. PET can identify suspicious locations within complex tumors that are most likely to contain important diagnostic and prognostic information.

Percutaneous Renal Biopsies for Small Renal Masses: Complex Tumors on Nephrometry Should Be the First Targets

OBJECTIVE

To assess the diagnostic yield, accuracy, and complications rate for computed tomography (CT)-guided renal biopsies for solid renal masses (SRM); to analyze predictive factors for diagnostic biopsies.

PATIENTS AND METHODS

We performed a single-center, retrospective study based on a pathologic database query for CT-guided, percutaneous renal biopsies. Inclusion criteria included presence of SRM; exclusion criteria included the presence of metastases, non-cT1a or higher cancer (> 4 cm), and non-CT-guided techniques. Of 119 patients who underwent renal biopsies, 40 (34%) were excluded from the study; 79 (66%) biopsy outcomes were analyzed. Clinical, radiologic (RENAL score), and pathologic features were reported. Differences between contributive and noncontributive biopsies were tested with Mann-Whitney U or chi-square tests, as appropriate. Multiple-variable analyses searching for predicting factors of biopsy contribution were performed with binary logistic regressions.

RESULTS

CT-guided renal biopsies for SRM present a high yield (88.6%) and high accuracy for differentiating malignant from benign tumors (96%). They are less accurate for histologic subtype (93%) and unreliable for Fuhrman grading (64%). CT-guided renal biopsy is safe (minor complication rate, 2.5%) and helped prevent unnecessary surgery in 30.4% of the cohort. Tumor complexity with high RENAL score was a predictive factor (P = .02) of contributive biopsy.

CONCLUSION

SRM biopsy is a safe, reliable procedure that can help determine the best treatment strategy for patients. It seems more beneficial for nephrometry complex tumors when surgical extirpation is more likely to be complicated. SRM biopsy might be encouraged in clinical practice for complex tumors.

The role of renal biopsy in small renal masses

Renal biopsy is being increasingly proposed as a diagnostic tool to characterize small renal masses (SRM). Indeed, the wide adoption of imaging in the diagnostic workup of many diseases had led to a substantial increased incidence of SRM (diameter ≤4 cm). While modern ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI) techniques have high sensitivity for detecting SRM, none is able to accurately and reliably characterize them in terms of histological features. This is currently of key importance in guiding clinical decision-making in some situations, and in these cases renal biopsy should be considered. In this review, we aim to summarize the technique, diagnostic performance, and predicting factors of nondiagnostic biopsy, as well as the future perspectives.

ACR Appropriateness Criteria indeterminate renal mass

Renal masses are increasingly detected in asymptomatic individuals as incidental findings. An indeterminate renal mass is one that cannot be diagnosed confidently as benign or malignant at the time it is discovered. CT, ultrasonography, and MRI of renal masses with fast-scan techniques and intravenous (IV) contrast are the mainstays of evaluation. Dual-energy CT, contrast-enhanced ultrasonography, PET/CT, and percutaneous biopsy are all technologies that are gaining traction in the characterization of the indeterminate renal mass. In cases in which IV contrast cannot be used, whether because of IV contrast allergy or renal insufficiency, renal mass classification with CT is markedly limited. In the absence of IV contrast, ultrasonography, MRI, and biopsy have some advantages. Owing to the low malignant and metastatic potential of small renal cell carcinomas (≤4 cm in diameter), active surveillance is additionally emerging as a diagnostic strategy for patients who have high surgical risk or limited life expectancy. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and application by the panel of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Growth Pattern of Clear Cell Renal Cell Carcinoma in Patients with Delayed Surgical Intervention: Fast Growth Rate Correlates with High Grade and May Result in Poor Prognosis

Objectives. Previous studies revealed an unclear correlation between the growth rate of renal cell carcinoma (RCC) and tumor grade and did not focus on certain histological subtype. This report investigated the correlation between the growth rate and tumor grade in clear cell RCC (ccRCC). Methods. We reviewed 60 patients with 61 ccRCC confirmed by delayed surgeries after at least 12 months of active surveillance. The linear growth rate (LGR), volumetric growth rate (VGR), and volume doubling time (VDT) were calculated, and their correlations with clinicopathologic characteristics were analyzed. Results. The mean LGR, VGR, and VDT were 0.86 (range 0–4.74) cm/year, 20.96 (range 0.31–211.93) cm³/year, and 667 (range 33–3321) days, respectively. ccRCCs with high grade had greater LGR (P < 0.001) and VGR (P = 0.001) and lower VDT (P = 0.017) than ccRCCs with low grade. Grade (OR = 5.185, P = 0.004) was the only independent risk factor of LGR >0.5 cm/year, and grade (OR = 3.006, P = 0.046) and initial size (OR = 0.392, P = 0.004) were independent risk factors of VDT <1 year. Five patients developed metastasis after surgery with LGR >0.5 cm/yr altogether; of them, four had cancer-related death by the last follow-up. Conclusions. Fast growth rate of ccRCC is significantly correlated with high tumor grade and may result in poor prognosis, especially for those with LGR >0.5 cm/yr.

Systematic Review and Meta-analysis of Diagnostic Accuracy of Percutaneous Renal Tumour Biopsy

CONTEXT

The role of percutaneous renal tumour biopsy (RTB) remains controversial due to uncertainties regarding its diagnostic accuracy and safety.

OBJECTIVE

We performed a systematic review and meta-analysis to determine the safety and accuracy of percutaneous RTB for the diagnosis of malignancy, histologic tumour subtype, and grade.

EVIDENCE ACQUISITION

Medline, Embase, and Cochrane Library were searched for studies providing data on diagnostic accuracy and complications of percutaneous core biopsy (CB) or fine-needle aspiration (FNA) of renal tumours. A meta-analysis was performed to obtain pooled estimates of sensitivity and specificity for diagnosis of malignancy. The Cohen kappa coefficient (κ) was estimated for the analysis of histotype/grade concordance between diagnosis on RTB and surgical specimen. Risk of bias assessment was performed (QUADAS-2).

EVIDENCE SYNTHESIS

A total of 57 studies recruiting 5228 patients were included. The overall median diagnostic rate of RTB was 92%. The sensitivity and specificity of diagnostic CBs and FNAs were 99.1% and 99.7%, and 93.2% and 89.8%, respectively. A good (κ = 0.683) and a fair (κ = 0.34) agreement were observed between histologic subtype and Fuhrman grade on RTB and surgical specimen, respectively. A very low rate of Clavien ≥ 2 complications was reported. Study limitations included selection and differential-verification bias.

CONCLUSIONS

RTB is safe and has a high diagnostic yield in experienced centres. Both CB and FNA have good accuracy for the diagnosis of malignancy and histologic subtype, with better performance for CB. The accuracy for Fuhrman grade is fair. Overall, the quality of the evidence was moderate. Prospective cohort studies recruiting consecutive patients and using homogeneous reference standards are required.

PATIENT SUMMARY

We systematically reviewed the literature to assess the safety and diagnostic performance of renal tumour biopsy (RTB). The results suggest that RTB has good accuracy in diagnosing renal cancer and its subtypes, and it appears to be safe. However, the quality of evidence was moderate, and better quality studies are required to provide a more definitive answer.

Accuracy of Percutaneous Core Biopsy in the Diagnosis of Small Renal Masses (≤ 4.0 cm): A Meta-analysis

Objective

To use meta-analysis to determine the accuracy of percutaneous core needle biopsy in the diagnosis of small renal masses (SMRs≤4.0 cm).

Materials and Methods

Studies were identified by searching PubMed, Embase, and the Cochrane Library database up to March 2013. Two of the authors independently assessed the study quality using QUADAS-2 tool and extracted data that met the inclusion criteria. The sensitivity, specificity, likelihood ratios, diagnostic odds ratio (DOR) and also summary receiver operating characteristic (SROC) curve were investigated and draw. Deek’s funnel plot was used to evaluate the publication bias.

Result

A total of 9 studies with 788 patients (803 biopsies) were included. Failed biopsies without repeated or aborted from follow-up/surgery result were excluded (232 patients and 353 biopsies). For all cases, the pooled sensitivity was 94.0% (95% CI: 91.0%, 95.0%), the pooled positive likelihood was 22.57 (95% CI: 9.20-55.34), the pooled negative likelihood was 0.09 (95% CI: 0.06-0.13), the pooled DOR was 296.52(95% CI: 99. 42-884.38). The area under the curve of SROC analysis was 0.959±0.0254.

Conclusion

Imaging-guided percutaneous core needle biopsy of small renal masses (SMRs≤4.0 cm) is highly accurate to malignant tumor diagnosis with unknown metastatic status and could be offered to some patients after clinic judgment prior to surgical intervention consideration.

Management of renal cell carcinoma presenting as inflammatory renal mass

Introduction:

Renal cell carcinoma (RCC) can have a wide spectrum of clinical presentations. In the immunocompromised patient fever and an inflammatory renal mass can harbor RCC.

Materials and Methods:

We reviewed the charts of patients who were managed at our department during 1998-2008 as renal abscess or perinephric collection. Renal ultrasound and subsequently abdominal CT was done. Medical treatment in the form of antibiotics, control of diabetes and drainage was done. Percutaneous or open biopsy, pus cultures, and histopathology were used to guide therapy. With a positive biopsy radical surgery was considered, while with a negative result a follow up CT was planned.

Results:

We identified 11 patients who had high fever, a renal abscess (in 4), or a suspicious mass with perinephric collection (in 7), and were eventually diagnosed to have RCC. Mean patient age was 66 years (53-82). 8 patients had uncontrolled diabetes. Five patients had a percutaneous drainage biopsy; of those two had a positive histopathology, the other three patients had a persistent enhancing mass on follow-up CT scan. Of this group three patients underwent radical nephrectomy. Another five patients had open drainage and biopsy, four patients had very poor performance status. One patient had radical surgery without the need for biopsy.

Conclusion:

In the elderly and immunocompromised patient renal cancer may present as renal abscess or perinephric collection. Histopathology and bacteriology are the mainstay of diagnosis. If biopsy was negative, follow up should include a CT scan to exclude any residual enhancing masses.

Tubulocystic renal cell carcinoma: a new radiological entity

Tubulocystic renal cell carcinoma (TC-RCC) is a recently identified renal malignancy. While approximately 100 cases of TC-RCC have been reported in the pathology literature, imaging features have not yet been clearly described. The purpose of this review is to describe the main radiologic features of this rare sub-type of RCC on ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), based jointly on the literature and findings from a multi-institutional retrospective HIPAA-compliant review of pathology and imaging databases. Using a combination of sonographic and CT/MRI features, diagnosis of TC-RCC appeared to be strongly suggested in many cases.

KEY POINTS

• Tubulocystic renal cell carcinoma is a new entity with typical imaging features • Diagnosis of tubulocystic renal cell carcinoma can be suggested preoperatively by imaging • Cystic renal lesions with high echogenicity may correspond to tubulocystic carcinoma.

Image-guided urological interventions: What the urologists must know

Advances in imaging technology, especially in the last two decades, have led to a paradigm shift in the field of image-guided interventions in urology. While the traditional biopsy and drainage techniques are firmly established, image-based stone management and endovascular management of hematuria have evolved further. Ablative techniques for renal and prostate cancer and prostate artery embolization for benign prostatic hypertrophy have evolved into viable alternative treatments. Many urologic diseases that were earlier treated surgically are now effectively managed using minimally invasive image-guided techniques, often on a day care basis using only local anesthesia or conscious sedation. This article presents an overview of the technique and status of various image-guided urological procedures, including recent emerging techniques.

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.

Initial experience with endoscopic ultrasound-guided fine needle aspiration of renal masses: indications, applications and limitations

CONTEXT

Tissue sampling of renal masses is traditionally performed via the percutaneous approach or laparoscopicaly. The utility of endoscopic ultrasound to biopsy renal lesions it remains unclear and few cases have been reported.

OBJECTIVES

To evaluate the feasibility and outcome of endoscopic ultrasound fine needle aspiration of renal tumors.

METHODS

Consecutive subjects undergoing attempted endoscopic ultrasound fine needle aspiration of a kidney mass after evaluation with computerized tomography or magnetic resonance.

RESULTS

Ten procedures were performed in nine male patients (median age 54.7 years) on the right (n = 4) and left kidney (n = 4) and bilaterally (n = 1). Kidney masses (median diameter 55 mm ; range 13-160 mm) were located in the upper pole (n = 3), the lower pole (n = 2) and the mesorenal region (n = 3). In two cases, the mass involved more than one kidney region. Surgical resection confirmed renal cell carcinoma in six patients in whom pre-operative endoscopic ultrasound fine needle aspiration demonstrated renal cell carcinoma. No complications were reported.

CONCLUSIONS

Endoscopic ultrasound fine needle aspiration appears as a safe and feasible procedure with good results and minimal morbidity.

Diagnostic potential of multidetector computed tomography for characterizing small renal masses

OBJECTIVES

To assess the potential of CT for characterizing small renal tumors.

METHODS

76 patients with <4 cm renal tumors underwent CT examination. The following parameters were assessed: presence of calcifications, densitometry on unenhanced and enhanced scans, washout percentage, urinary tract infiltration, star-shaped scar, and paradoxical effect.

RESULTS

Calcifications were found in 7/56 (12.5%) carcinomas. Clear cell carcinomas were as follows: mean density 183.5 HU (arterial phase), 136 HU (portal phase), and 94 HU (delayed phase), washout 34.3%; chromophobe carcinomas were as follows: mean density 135 HU (arterial phase), 161 HU (portal phase), and 148 HU (delayed phase), washout 28%; papillary carcinomas were as follows: mean density 50.3 HU (arterial phase), 60 HU (portal phase), and 58.1 HU (delayed phase), washout 2.7%. In 2/56 (3.6%) cases urinary tract infiltration was found. Oncocytomas were as follows: mean density 126.5 HU (arterial phase), 147.5 HU (portal phase), and 115.5 HU (delayed phase), washout 28.6%. On unenhanced scans, angiomyolipomas were as follows: density values <30 HU in 12/12 (100%) of cases and on enhanced scans: mean density 78 HU (arterial phase), 128 HU (portal phase), and 80 HU (delayed phase), washout 50%.

CONCLUSIONS

Intralesional calcifications and urinary tract infiltration are suggestive for malignancy, with the evidence of adipose tissue for angiomyolipomas and a modest increase in density with a reduced washout for papillary carcinomas. The intralesional density on enhanced scans, peak enhancement, and washout do not seem significant for differentiating clear cell, chromophobe carcinomas, angiomyolipomas, and oncocytomas.

The diagnostic accuracy of percutaneous renal needle core biopsy and its potential impact on the clinical management of renal cortical neoplasms

CONTEXT

While biopsies are now increasingly being performed for the diagnosis of renal cortical neoplasms, the influence of the rendered pathological diagnoses on the clinical management is only rarely documented.

OBJECTIVES

To report our experience with consecutively performed renal biopsies and the potential impact of the diagnosis on subsequent clinical management.

DESIGN

Material from needle biopsies performed consecutively at our institution between 2006 and 2011 was reviewed. The influence of the reported pathology results on the clinical management was determined from patient follow-up medical record review.

RESULTS

In total, 218 percutaneous biopsies for renal masses were performed during this period. Among them, 181 (83%) yielded neoplastic tissue, including 81 clear cell renal cell carcinomas, 29 low-grade oncocytic neoplasms, 7 papillary renal cell carcinomas, 5 clear cell papillary renal cell carcinomas, 5 angiomyolipomas, and 14 urothelial carcinomas. Fourteen additional cases (6%) contained lesional material from clinically known nonneoplastic processes, for a total diagnostic yield of 89%. Twenty-three (11%) were nonrepresentative of lesional tissue. In 10 of these, repeat biopsies or resections established the diagnosis of renal tumors. Biopsy diagnosis was confirmed in 29 of 30 cases (97%) on subsequent nephrectomy. Following the biopsy diagnosis, there were significant differences in the clinical management; overall, 79% of clear cell renal cell carcinomas received therapeutic interventions, and 17% were put on active surveillance. In contrast, 77% of the benign or low-grade lesions were put on active surveillance.

CONCLUSIONS

Accurate and specific diagnosis can be rendered on renal core biopsy in most renal tumors, and the biopsy diagnosis can have a definitive role in their clinical management.

Diagnostic significance of biopsies in renal masses

Introduction

We investigated the reliability and mapping of percutaneous needle core biopsies in the kidney in histopathological diagnosis of renal masses particularly for those with suspicious radiologic appearance in an attempt to prevent unnecessary nephrectomies.

Material and methods

Overall, 96 cases were included in our study that underwent radical nephrectomy or partial nephrectomy due to renal mass between November 2007 – March 2010. Ex–vivo biopsies 1 cm apart were obtained from the peripheral region of the mass. Additionally, half of these peripheral biopsies were obtained from the central region of the mass. Diagnostic yield of the biopsy cores were correlated. Sensitivity and specificity of peripheral and central biopsies in differentiating benign and malignant tissues were calculated.

Results

Sensitivity and specificity in differentiating malignant lesions were 93% and 87%, and 90% and 93% for peripheral and central biopsies, respectively. Positive and negative predictive values were 97% and 68%, and 98% and 64% for peripheral biopsies and central biopsies, respectively. Hazard ratio for cigarette smoking and presence of necrosis on CT scans were 4.76 (CI 1, 6–14.3; p = 0.04) and 3.32 (CI 1,2–9.2; p = 0.017) and 3.71 (CI 1.3–10.7; p = 0.013) and 3,51 (CI 1.3–9.6; p = 0.012) for peripheral and central biopsies, respectively.

Conclusions

Kidney biopsies can be performed in suspicious renal masses of central and peripheral biopsies with similar efficacy.

Heterogeneity and renal mass biopsy: a review of its role and reliability

Increased abdominal imaging has led to an increase in the detection of the incidental small renal mass (SRM). With increasing recognition that the malignant potential of SRMs is heterogeneous, ranging from benign (15%-20%) to aggressive (20%), enthusiasm for more conservative management strategies in the elderly and infirmed, such as active surveillance (AS), have grown considerably. As the management of the SRM evolves to incorporate ablative techniques and AS for low risk disease, the role of renal mass biopsy (RMB) to help guide individualized therapy is evolving. Historically, the role of RMB was limited to the evaluation of suspected metastatic disease, renal abscess, or lymphoma. However, in the contemporary era, the role of biopsy has grown, most notably to identify patients who harbor benign lesions and for whom treatment, particularly the elderly or frail, may be avoided. When performing a RMB to guide initial clinical decision making for small, localized tumors, the most relevant questions are often relegated to proof of malignancy and documentation (if possible) of grade. However, significant intratumoral heterogeneity has been identified in clear cell renal cell carcinoma (ccRCC) that may lead to an underestimation of the genetic complexity of a tumor when single-biopsy procedures are used. Heterogeneous genomic landscapes and branched parallel evolution of ccRCCs with spatially separated subclones creates an illusion of clonal dominance when assessed by single biopsies and raises important questions regarding how tumors can be optimally sampled and whether future evolutionary tumor branches might be predictable and ultimately targetable. This work raises profound questions concerning the genetic landscape of cancer and how tumor heterogeneity may affect, and possibly confound, targeted diagnostic and therapeutic interventions. In this review, we discuss the current role of RMB, the implications of tumor heterogeneity on diagnostic accuracy, and highlight promising future directions.

Current status of renal biopsy for small renal masses

Small renal masses (SRMs) are defined as radiologically enhancing renal masses of less than 4 cm in maximal diameter. The incidence of renal cell carcinoma (RCC) has increased in recent years, which is mainly due to the rise in incidental detection of localized SRMs. However, the cancer-specific mortality rate is not increasing. This discrepancy may be dependent on the indolent nature of SRMs. About 20% of SRMs are benign, and smaller masses are likely to have pathologic characteristics of low Fuhrman grade and clear cell type. In addition, SRMs are increasingly detected in elderly patients who are likely to have comorbidities and are a high-risk group for active treatment like surgery. As the information about the nature of SRMs is improved and management options for SRMs are expanded, the current role of renal mass biopsy for SRMs is also expanding. Traditionally, renal mass biopsy has not been accepted as a standard diagnostic tool in the clinical scenario because of several issues about safety and accuracy. However, current series on SRM biopsy have reported high diagnostic accuracy with rare complications. Studies of modern SRM biopsy have reported diagnostic accuracy greater than 90% with very high specificity. Also, current series have shown very rare morbid cases caused by renal mass biopsy. Currently, renal biopsy of SRMs can be recommended in most cases except when patients have imaging or clinical characteristics indicative of pathology and in cases in which conservative management is not considered.

Multiparametric magnetic resonance imaging for the differentiation of low and high grade clear cell renal carcinoma

PURPOSE

To retrospectively evaluate the ability of magnetic resonance (MR) imaging to differentiate low from high Fuhrman grade renal cell carcinoma (RCC).

MATERIALS AND METHODS

MR images from 80 consecutive pathologically proven RCC (57 clear cell, 16 papillary and 7 chromophobe) were evaluated. Double-echo chemical shift, dynamic contrast-enhanced T1- and T2-weighted images and apparent diffusion coefficient (ADC) maps were reviewed independently. Signal intensity index (SII), tumour-to-spleen SI ratio (TSR), ADC ratio, wash-in (WiI) and wash-out indices (WoI) between different phases were calculated and compared to pathological grade and size. The Fuhrman scoring system was used. Low grade (score ≤ 2) and high grade (score ≥ 3) tumours were compared using univariate and multivariate analyses.

RESULTS

No associations between grade and imaging factors were found for papillary and chromophobe RCCs. For clear cell RCCs, there was a significant association between the grade and parenchymal WiI (WiI2) (P = 0.02) or ADCr (P = 0.03). A significant association between tumour grade and size (P = 0.01), WiI2 (P = 0.02) and ADCr (P = 0.05) remained in multivariate analysis.

CONCLUSIONS

Multiparametric MRI can be used to accurately differentiate low Fuhrman grade clear cell RCC from high grade. High Fuhrman grade (≥ 3) RCCs were larger, had lower parenchymal wash-in indices and lower ADC ratios than low grade.

KEY POINTS

• Fuhrman grade of clear cell RCC can be differentiated with multiparametric MR imaging. • Fuhrman grade significantly differed for size, parenchymal wash-in index and ADC ratio. • No significant associations were found for papillary and chromophobe renal cell carcinoma.

Performance of intra-procedural 18-fluorodeoxyglucose PET/CT-guided biopsies for lesions suspected of malignancy but poorly visualized with other modalities

PURPOSE

We sought to evaluate the safety and the diagnostic success rate of percutaneous biopsies performed under intra-procedural (18)F-deoxyglucose (FDG) positron-emission tomography/computed tomography (PET/CT) guidance for lesions difficult to see with conventional cross-sectional imaging.

METHODS

From 2011 to 2013, consecutive clinically indicated percutaneous PET/CT-guided biopsies of 106 masses (mean size, 3.3 cm; range, 0.7-15.9 cm; SD, 2.9 cm) in bones (n = 33), liver (n = 26), soft tissues (n = 18), lung (n = 15) and abdomen (n = 14) were reviewed. The biopsy procedures were performed following injection of a mean of 255 MBq (SD, 74) FDG. Mean maximal standardized uptake value (SUV) of lesions was 8.8 (SD, 6.3). A systematic review of the histopathological results and outcomes was performed.

RESULTS

Biopsies were positive for malignancy in 76 cases (71.7%, 76/106) and for benign tissue in 30 cases (28.3%, 30/106). Immediate results were considered adequate for 100 PET/CT biopsies (94.3%, 100/106) requiring no further exploration, and for the six others (5.7%, 6/106) benign diagnoses were confirmed after surgery (n = 4) or follow-up (n = 2). The consequent overall sensitivity and the diagnostic success of biopsy were therefore 100%. No significant differences in terms of detection of malignancy were observed between the different locations. Lesions > 2 cm or with SUV > 4 were not significantly more likely to be malignant. Complications occurred after four biopsies (3.7%, 4/106).

CONCLUSION

Intra-procedural PET/CT guidance appears as a safe and effective method and allows high diagnostic success of percutaneous biopsies for metabolically active lesions.

Role of percutaneous needle biopsy for renal masses

The role of percutaneous renal mass biopsy has expanded considerably in the past 10 years. The incidence of incidentally detected small (< 4 cm) solid renal masses is on the rise, and despite a commensurate increase in nephron-sparing treatment, the mortality rate from renal cell carcinoma remains the same. Earlier detection and treatment have not had dramatic effects on population outcome, implying that not all small renal masses will grow to be life-limiting. Indeed, many small solid renal masses are benign, and among those that are malignant, not all share the same malignant behavior. Percutaneous biopsy provides a minimally invasive method for discriminating benign from malignant renal masses, and portends the potential for stratifying malignant risk. With recent improvements in image-guided equipment and technique, percutaneous renal mass biopsy can be performed safely and effectively, with a low complication rate (< 5%) and a high diagnostic yield (> 90%).

Routinely performed multiparametric magnetic resonance imaging helps to differentiate common subtypes of renal tumours

OBJECTIVES

To retrospectively evaluate the ability of multiparametric magnetic resonance (MR) imaging to differentiate renal tumours.

METHODS

MR images from 100 consecutive pathologically proven solid renal tumours without macroscopic fat [57 clear cell, 16 papillary and 7 chromophobe renal cell carcinomas (RCCs), 16 oncocytomas and 4 minimal fat angiomyolipomas (AMLs)] between 2009 and 2012 were evaluated. Two radiologists blinded to pathology results independently reviewed double-echo chemical shift, dynamic contrast-enhanced T1- and T2-weighted images and apparent diffusion coefficient (ADC) maps. Signal intensity index (SII), tumour-to-spleen SI ratio (TSR), ADC ratio, wash-in (WiI) and wash-out indices (WoI) between different phases were calculated.

RESULTS

There were significant differences between papillary RCCs and other renal tumours for arterial WiI (P < 0.001), initial WoI (P = 0.006) and ADC ratio (P < 0.001); between chromophobe RCCs and oncocytomas for TSR (P = 0.02), parenchymal WiI (P = 0.03), late WiI (P = 0.02), initial WoI (P = 0.03) and late WoI (P = 0.04); and between clear cell RCCs and oncocytomas for SII (P = 0.01) and parenchymal WiI (P = 0.01). Papillary RCCs were distinguished from other tumours (sensitivity 37.5 %, specificity 100 %) and oncocytomas from chromophobe RCCs (sensitivity 25 %, specificity 100 %) and clear cell RCCs (sensitivity 100 %, specificity 94.2 %).

CONCLUSION

MR imaging provides criteria able to accurately distinguish papillary RCCs from other tumours and oncocytomas from chromophobe and clear cell RCCs.

KEY POINTS

• Multiparametric MR parameters accurately distinguish papillary RCCs with high specificity (100 %). • Oncocytomas can be distinguished from chromophobe RCCs with high specificity (100 %). • Oncocytomas can be distinguished from clear cell RCCs with high specificity (94.2 %). • In oncocytomatosis, imaging follow-up with such parameters analysis could be promoted.

Histopathologic findings of small renal tumor biopsies performed immediately after cryoablation therapy: a retrospective study of 50 cases

OBJECTIVES

To evaluate the histopathology of small renal tumor biopsies following cryoablation.

METHODS

We retrospectively evaluated small renal tumor biopsy specimens after cryoablation treatment for renal cell carcinoma and determined the ability to differentiate tumor types, effect on nuclear grading, immunohistochemical staining, and if the number of freeze cycles affected interpretation.

RESULTS

Of the biopsy specimens, 66% were diagnostic of tumor and 34% showed normal renal parenchyma. Tumor subtype was determined in 91% of diagnostic cases. Nuclear grading was affected due to freeze effect, complicating the assessment of chromatin pattern and nucleolar details at low magnification. In particular, the distinction between Fuhrman nuclear grades I and II was compromised; these were designated as low nuclear grade. Immunohistochemical staining was retained similar to untreated tumors. Tumor subtyping was not affected after one or two freeze cycles.

CONCLUSIONS

Biopsies performed immediately after cryoablation can be used to render an optimal histologic diagnosis.

Sonographically guided transhepatic core biopsies of right renal and adrenal masses: safety and short-term follow-up

OBJECTIVES

The purpose of this study was to retrospectively evaluate the accuracy and safety of sonographically guided transhepatic biopsies of right upper renal and adrenal masses.

METHODS

Ten sonographically guided transhepatic biopsies were performed in 10 patients with 6 right upper renal masses and 4 right adrenal masses that were invisible or inaccessible via an extrahepatic route. The control population comprised 19 sonographically guided extrahepatic biopsies that were performed in 19 patients with 18 right upper renal masses and 1 right adrenal mass. Transhepatic and extrahepatic biopsies were compared with respect to the diagnostic and complication rates. The mass sizes, biopsy distances, numbers and lengths of cores, and biopsy durations were also compared.

RESULTS

The diagnostic rates of transhepatic and extrahepatic biopsies were 90% (9 of 10) and 89% (17 of 19), respectively (P > .999). The complication rates of transhepatic and extrahepatic biopsies were 10% (1 of 10) and 21% (4 of 19; P > .999). None of these biopsies resulted in major complications. The mean mass sizes, biopsy distances, and numbers of cores ± SD for transhepatic and extrahepatic biopsies were 33.0 ± 14.3 and 46.9 ± 18.5 mm, 100.5 ± 17.9 and 76.5 ± 9.9 mm, and 2.7 ± 0.9 and 4.0 ± 0.7, respectively (P = .046, .038, and .001). However, the core lengths and biopsy durations were not significantly different between these biopsies (P = .91 and .077).

CONCLUSIONS

Sonographically guided transhepatic core biopsies appear to be feasible and safe procedures for the histologic diagnosis of right upper renal and adrenal masses that are either invisible or inaccessible via an extrahepatic route.