Cystic renal cell carcinoma carries an excellent prognosis regardless of tumor size

Characteristics of high frame frequency contrast-enhanced ultrasound in renal tumors

OBJECTIVE

This study aims to analyze the characteristics of high frame rate contrast-enhanced ultrasound (H-CEUS) in renal lesions and to improve the ability for differential diagnosis of renal tumors.

METHODS

A total of 140 patients with renal lesions underwent contrast-enhanced ultrasound (CEUS) examination in the First Affiliated Hospital of Nanchang University from July 2022 to July 2023. Based on the tumor pathology and the results of enhanced CT, tumor patients were divided into malignant and benign groups. All subjects were examined using gray-scale ultrasound, conventional contrast-enhanced ultrasound (C-CEUS), and H-CEUS, and their dynamic images were recorded. Two radiologists independently analyzed and recorded the results of ultrasound, C-CEUS, and H-CEUS images and statistically analyzed the features of C-CEUS and H-CEUS images. The independent sample t-test was used to compare the difference in age and maximum diameter of nodules between the benign and malignant groups. The χ2 test was used to compare the sex, mode of operation, gray-scale ultrasound characteristics, and enhancement characteristics of the two CEUS modes (enhancement mode, regression mode, enhancement degree, enhancement uniformity, enhancement or not, enhancement direction, post-enhancement boundary and range, and pseudocapsule) between the benign and malignant groups. The difference in vascular morphology of malignant nodules of varying sizes under two angiographic modes.

RESULTS

There were significant differences in gender (χ2 = 10.408, P = 0.001), mode of operation (χ2 = 47.089, P < 0.001), nodule composition (χ2 = 7.481, P = 0.003), nodule echo (χ2 = 20.926, P < 0.001), necrosis (χ2 = 31.343, P < 0.001) and nodule blood flow (χ2 = 9.006, P = 0.029) between the benign and malignant groups. There were significant differences in the regression model (χ2 = 6.782, P = 0.034) and enhancement direction (χ2 = 13.771, P = 0.001) between the two radiographic techniques in the malignant group. There was a significant difference in the enhancement uniformity between the two CEUS techniques in the benign group (χ2 = 8.264, P = 0.004). There was a significant difference between the two CEUS techniques in displaying the vascular morphology in the malignant group with the maximum diameter of nodules ≤ 4.0 cm (χ2 = 11.421, P < 0.022). However, there was no significant difference between the two techniques in the malignant group with the maximum diameter of nodules > 4.0 cm.

CONCLUSION

Increasing the frame rate of ultrasound images is helpful to accurately display the enhanced features and vascular morphology of renal tumors, especially for malignant tumors with a maximum diameter of ≤ 4.0 cm. Thus, H-CEUS can make up for the limitation of CEUS with regard to the display of vascular morphology.

Development and validation of a nomogram for predicting the impact of tumor size on cancer-specific survival of locally advanced renal cell carcinoma: a SEER-based study

This study was aimed to integrate tumor size with other prognostic factors into a prognostic nomogram to predict cancer-specific survival (CSS) in locally advanced (≥pT3a Nany M0) renal cell carcinoma (RCC) patients. Based on the Surveillance, Epidemiology, and End Results (SEER) database, 10,800 patients diagnosed with locally advanced RCC were collected. They were randomly divided into a training cohort (n = 7,056) and a validation cohort (n = 3,024). X-tile program was used to identify the optimal cut-off value of tumor size and age. The cut-off of age at diagnosis was 65 years old and 75 years old. The cut-off of tumor size was 54 mm and 119 mm. Univariate and multivariate Cox regression analyses were performed in the training cohort to identify independent prognostic factors for construction of nomogram. Then, the nomogram was used to predict the 1-, 3- and 5-year CSS. The performance of nomogram was evaluated by using concordance index (C-index), area under the Subject operating curve (AUC) and decision curve analysis (DCA). Moreover, the nomogram and tumor node metastasis (TNM) staging system (AJCC 8th edition) were compared. 10 variables were screened to develop the nomogram. The area under the receiver operating characteristic (ROC) curve (AUC) indicated satisfactory ability of the nomogram. Compared with the AJCC 8th edition of TNM stage, DCA showed that the nomogram had improved performance. We developed and validated a nomogram for predicting the CSS of patients with locally advanced RCC, which was more precise than the AJCC 8th edition of TNM staging system.

Multiparametric MRI-Based Machine Learning Models for the Characterization of Cystic Renal Masses Compared to the Bosniak Classification, Version 2019: A Multicenter Study

RATIONALE AND OBJECTIVE

Accurate differentiation between benign and malignant cystic renal masses (CRMs) is challenging in clinical practice. This study aimed to develop MRI-based machine learning models for differentiating between benign and malignant CRMs and compare the best-performing model with the Bosniak classification, version 2019 (BC, version 2019).

METHODS

Between 2009 and 2021, consecutive surgery-proven CRM patients with renal MRI were enrolled in this multicenter study. Models were constructed to differentiate between benign and malignant CRMs using logistic regression (LR), random forest (RF), and support vector machine (SVM) algorithms, respectively. Meanwhile, two radiologists classified CRMs into I-IV categories according to the BC, version 2019 in consensus in the test set. A subgroup analysis was conducted to investigate the performance of the best-performing model in complicated CRMs (II-IV lesions in the test set). The performances of models and BC, version 2019 were evaluated using the area under the receiver operating characteristic curve (AUC). Performance was statistically compared between the best-performing model and the BC, version 2019.

RESULTS

278 and 48 patients were assigned to the training and test sets, respectively. In the test set, the AUC and accuracy of the LR model, the RF model, the SVM model, and the BC, version 2019 were 0.884 and 75.0%, 0.907 and 83.3%, 0.814 and 72.9%, and 0.893 and 81.2%, respectively. Neither the AUC nor the accuracy of the RF model that performed best were significantly different from the BC, version 2019 (P = 0.780, P = 0.065). The RF model achieved an AUC and accuracy of 0.880 and 81.0% in complicated CRMs.

CONCLUSIONS

The MRI-based RF model can accurately differentiate between benign and malignant CRMs with comparable performance to the BC, version 2019, and has good performance in complicated CRMs, which may facilitate treatment decision-making and is less affected by interobserver disagreements.

Comparison of partial nephrectomy and radical nephrectomy for cystic renal cell carcinoma: a SEER-based and retrospective study

Cystic renal cell carcinoma (cRCC) is uncommon and surgical indication remains controversial. We compared radical nephrectomy (RN) with partial nephrectomy (PN) in patients with cRCC using data from the Surveillance, Epidemiology and End Results (SEER) database and a retrospective cohort including 106 cRCC patients hospitalized in Ruijin and Renji Hospitals from 2013 to 2022. The baseline characteristics between RN and PN groups in both cohorts were adjusted by propensity score-matching (PSM). A total of 640 patients were included in the SEER cohort. Before PSM, PN group in the SEER cohort had a lower level of T stage (p < 0.001) and comprised more Caucasians (p < 0.001). After PSM, RN was associated with worse overall survival (p < 0.001) and cancer-specific survival (p = 0.006) in contrast to PN. In the Chinese cohort, 86 patients who underwent PN and 20 patients who underwent RN were finally included. The mean proportions of estimated glomerular filtration rate preserved after RN were worse than PN. Therefore, PN should be preferred in cRCC patients.

Cystic Renal Masses: Old and New Paradigms

Cystic renal masses describe a spectrum of lesions with benign and/or malignant features. Cystic renal masses are most often identified incidentally with the Bosniak classification system stratifying their malignant potential. Solid enhancing components most often represent clear cell renal cell carcinoma yet display an indolent natural history relative to pure solid renal masses. This has led to an increased adoption of active surveillance as a management strategy in those who are poor surgical candidates. This article provides a contemporary overview of historical and emerging clinical paradigms in the diagnosis and management of this distinct clinical entity.

Volumetric Quantitative Contrast-enhanced Ultrasonography Evaluation of Complex Renal Cysts: An Adjunctive Metric to the Bosniak Classification System to Predict Malignancy

BACKGROUND

Management of complex renal cysts is guided by the Bosniak classification system, which may be inadequate for risk stratification of patients for intervention. Fractional tumor vascularity (FV) calculated from volumetric contrast-enhanced ultrasound (CEUS) images may provide additional useful information.

OBJECTIVE

To evaluate CEUS and FV calculation for risk stratification of patients with complex renal cysts.

DESIGN, SETTING, AND PARTICIPANTS

This was a pilot prospective study with institutional review board approval involving patients undergoing surgery for Bosniak IIF-IV complex renal cysts. CEUS was performed preoperatively on the day of surgery with two-dimensional (2D) and three-dimensional (3D) imaging and sulfur hexafluoride lipid-type A microspheres as the ultrasound contrast agent.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

A custom MATLAB program was used to select regions of interest on CEUS scans. FV was calculated according to FV = 1 - (total nonenhancing area/total lesion area). We assessed the ability of 2D- and 3D-derived percentage FV (2DFV%, and 3DFV%) and Bosniak classification schemes (pre-2019 [P2019B] and post-2019 [B2019]) to predict malignancy, aggressive histology, and upstaging on surgical pathology. Performance was assessed as area under the receiver operating characteristic curve (AUC).

RESULTS AND LIMITATIONS

Twenty eligible patients were included in final analysis, of whom 85% (n = 17) had Bosniak IV cysts and 85% (n = 17) had malignant disease on final pathology. Four (24%) of the malignant lesions were International Society of Urological Pathology grade 3-4. The AUC for predicting malignancy was 0.980, 0.824, 0.863, and 0.824 with P2019B, B2019, 2DFV%, and 3DFV%, respectively. When the Bosniak classification was combined with FV%, three models had an AUC of 1, while the combined 2DFV% + B2019 model had AUC of 0.980.

CONCLUSIONS

FV is a novel metric for evaluating complex cystic renal masses and enhances the ability of the Bosniak classification system to predict malignancy. This metric may serve as an adjunct in risk stratification for surgical intervention. Further prospective evaluation is warranted.

PATIENT SUMMARY

Cysts in the kidney are currently classified using a scheme called the Bosniak system. We assessed measurement of the percentage of vascular tissue (called fractional vascularity) in cysts on a special type of ultrasound scan. This promising test adds information when combined with the Bosniak system and can help in guiding appropriate treatment.

Active surveillance versus initial surgery in the long-term management of Bosniak IIF-IV cystic renal masses

There may be surgical overtreatment of complex cystic renal masses (CRM). Growing evidence supports active surveillance (AS) for the management for Bosniak IIF-III CRMs. We aimed to evaluate and compare oncological and pathological outcomes of Bosniak IIF-IV CRMs treated by initial surgery (IS) or AS. We identified retrospectively 532 patients with CRM counseled during 2006-2017. IS and AS were delivered to, respectively, 1 and 286 patients in Bosniak IIF, to 54 and 85 patients in III and to 85 and 21 patients in Bosniak IV. Median follow-up was 66 months (IQR 50-96). Metastatic progression occurred for 1 (0.3%) AS patient in Bosniak IIF, 1 IS (1.8%) and 1 AS (1.2%) patient in Bosniak III and 5 IS (3.5%) patients in Bosniak IV, respectively. Overall 5-year metastasis-free survival was 98.9% and cancer-specific survival was 99.6% without statistically significant difference between IS and AS in Bosniak IIF-IV categories. AS did not increase the risk of metastatic spread or cancer-specific mortality in patients with Bosniak IIF-IV. Our data indicate AS in Bosniak IIF and III is safe. Surgery is the primary treatment for Bosniak IV due to its high malignancy rate.

Active Surveillance of Renal Masses: The Role of Radiology

Active surveillance of renal masses, which includes serial imaging with the possibility of delayed treatment, has emerged as a viable alternative to immediate therapeutic intervention in selected patients. Active surveillance is supported by evidence that many benign masses are resected unnecessarily, and treatment of small cancers has not substantially reduced cancer-specific mortality. These data are a call to radiologists to improve the diagnosis of benign renal masses and differentiate cancers that are biologically aggressive (prompting treatment) from those that are indolent (allowing treatment deferral). Current evidence suggests that active surveillance results in comparable cancer-specific survival with a low risk of developing metastasis. Radiology is central in this. Imaging is used at the outset to estimate the probability of malignancy and degree of aggressiveness in malignant masses and to follow up masses for growth and morphologic change. Percutaneous biopsy is used to provide a more definitive histologic diagnosis and to guide treatment decisions, including whether active surveillance is appropriate. Emerging applications that may improve imaging assessment of renal masses include standardized assessment of cystic and solid masses and radiomic analysis. This article reviews the current and future role of radiology in the care of patients with renal masses undergoing active surveillance.

Using Contrast-Enhanced Ultrasound in Addition to Cross-Sectional Imaging for Indeterminate Renal Cysts May Lead to Overclassification in Bosniak III Category: A Case-Control Study

INTRODUCTION

Indeterminate renal cysts may require several imaging modalities before clinical decision. The aim of this study was to investigate the effect of the imaging modality used to characterize indeterminate renal cysts on the pathological findings after surgical resection.

METHODS

From our institutional database, we identified all patients surgically treated for Bosniak III renal masses between January 2008 and January 2018. All complex renal cysts were characterized with a combination of computed tomography (CT) and/or magnetic resonance imaging (MRI), and/or contrast-enhanced ultrasound (CEUS) and discussed during a multidisciplinary tumor board. Potential association between clinical/radiological characteristics and the pathological findings were investigated, using univariate and multivariate analyses.

RESULTS

Of the 52 renal cystic lesions surgically removed, with a preoperative diagnosis of Bosniak III renal cyst, 19 (37%) were malignant and 33 (63%) were benign. The proportion of malignant lesions decreased from 47% when the renal cyst was characterized with cross-sectional imaging (CT and/or MRI) to 17% when the diagnosis required CEUS in addition to cross-sectional imaging. In multivariate analysis, prior history of renal cell carcinoma was associated with a higher risk of malignancy (p = 0.016) and diagnosis made with CEUS was associated with a lower risk of malignancy (p = 0.040).

CONCLUSION

We found that using CEUS in addition to cross-sectional imaging to characterize indeterminate renal cysts tends to redefine Bosniak III as lesions with a lower risk of malignancy and can lead to overclassification.

Contrast-enhanced Ultrasound for Diagnosis of Renal Cystic Mass

BACKGROUND

Cystic Renal Cell Carcinoma (CRCC) is often challenging to differentiate from complex cysts with sonographic manifestations of renal carcinoma. Contrast-Enhanced Ultrasound (CEUS) is a new technology, and its clinical utility in the diagnosis of renal cystic mass has not been established.

OBJECTIVE

To analyze the characteristics of CEUS of renal cystic masses and to explore the clinical significance and value of CEUS in the diagnosis of CRCC.

METHODS

This study was a retrospective study. A total of 32 cystic masses from January 2018 to December 2019 were selected. The images of conventional ultrasound (US) and CEUS were confirmed via surgical pathology. The routine US was used to observe the location, shape, size, boundary, cyst wall, internal echo, and blood supply of each cystic mass. CEUS observed contrast enhancement of the cyst wall, cystic septa, and solid nodules of cystic masses.

RESULTS

There were 26 cases of CRCC, 5 cases of renal cysts, and 1 case of renal tuberculosis. The enhancement pattern, degree of enhancement, and pseudocapsular sign by CEUS in benign and malignant masses had statistically significant differences (P<.05). In the diagnosis of CRCC, the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were 92.3%, 83.3%, 90.6%, 96.0%, and 71.4% for CEUS; 57.6%, 66.7%, 59.3%, 88.2%, and 26.7% for conventional US, respectively. CEUS had a higher sensitivity and accuracy than the conventional US (P<.05). However, the diagnostic specificity, positive predictive value, and negative predictive value of the two methods were not significantly different (P>.05).

CONCLUSION

CEUS is more accurate in the diagnosis of renal cystic masses, and it can be used as an effective imaging method.

Malignant ascites following radical nephrectomy for cystic renal cell carcinoma

A 69-year-old man with a history of laparoscopic radical nephrectomy for papillary renal cell carcinoma presented with a 1-week history of generalised abdominal pain, distension and loss of appetite. Clinical examination and CT imaging demonstrated ascites associated with peritoneal nodules, raising the possibility of metastatic disease. Immunochemistry staining from ascites fluid cytology confirmed renal cell carcinoma. Following multidisciplinary discussions, the patient was commenced on a small-molecule tyrosine kinase inhibitor.

Imaging evaluation of hereditary renal tumors: a pictorial review

More than 10 hereditary renal tumor syndromes (HRTSs) and related germline mutations have been reported with HRTS-associated renal and extrarenal manifestations with benign and malignant tumors. Radiologists play an important role in detecting solitary or multiple renal masses with or without extrarenal findings on imaging and may raise the possibility of an inherited predisposition to renal cell carcinoma, providing direction for further screening, intervention and surveillance of the patients and their close family members before the development of potentially lethal renal and extrarenal tumors. Renal cell carcinomas (RCCs) associated with von Hippel-Lindau disease are typically slow growing while RCCs associated with HRTSs, such as hereditary leiomyomatosis and renal cell carcinoma syndrome, are highly aggressive. Therefore, radiologists need to be familiar with clinical and imaging findings of renal and extrarenal manifestations of HRTSs. This article reviews clinical and imaging findings for the evaluation of patients with well-established HRTSs from a radiologist's perspective to facilitate the clinical decision-making process for patient management.

Computed tomography features predicting aggressiveness of malignant parenchymal renal tumors suitable for partial nephrectomy

The aim of this study was to identify and standardize computed tomography (CT) features having a potential role in predicting aggressiveness of malignant parenchymal renal tumors suitable for partial nephrectomy (PN). We performed a non-systematic review of the recent literature to evaluate the potential impact of CT variables proposed by the Society of Abdominal Radiology Disease-Focused Panel on Renal Cell Carcinoma in predicting aggressiveness of newly diagnosed malignant parenchymal renal tumors. The analyzed variables were clinical tumor size, tumor growth rate, enhancement characteristics, amount of cystic component, polar and capsular location, tumor margins and distance between tumor and renal sinus. Unfavorable behavior was defined as: 1) renal cell carcinoma (RCC) with stage ≥pT3; 2) nuclear grade 3 or 4; 3) presence of sarcomatoid de-differentiation; or 4) non-clear cell subtypes with unfavorable prognosis (type 2 papillary RCC, collecting duct or renal medullary carcinoma, unclassified RCC). Beyond clinical tumor size, tumor growth rate, enhancement characteristics, amount of cystic component, tumor margins and distance between tumor and renal sinus are highly relevant features predicting an unfavorable behavior. Moreover, several studies supported the role of necrosis as preoperative predictor of tumor aggressiveness. Peritumoral and intratumoral vasculature as well as capsule status are emerging variables that need to be further evaluated. Tumor size, enhancement characteristics, tumor margins and distance to the renal sinus are highly relevant CT features predicting biological aggressiveness of malignant parenchymal renal tumors. Combination of these parameters might be useful to generate tools to predict the unfavorable behavior of renal tumors suitable for PN.

Concomitant Drug Treatment and Elimination in the RCC-affected Kidneys: Can We Kill Two Birds with One Stone?

BACKGROUND

The kidneys are vital organs acting as the body's filters that eliminate drugs and other waste products from the body. For effective cancer therapy, a delicate balance is required in the drug treatment and its elimination, which is critical for drug accumulation, toxicity, and kidney malfunction. However, how renal cell carcinoma (RCC) affects the kidneys in safely eliminating the byproducts of drug treatments in patients with severely dysregulated kidney functions had remained elusive. Recent advancements in dose adjustment have added to our understanding regarding how drug treatments could be effectively regulated in aberrant kidney cells, driving safe elimination and reducing drug accumulation and toxicity at the right time and space. Dose adjustment is the only standard systemic way applicable; however, it presents certain limitations. There is significant room for developing new strategies and alternatives to improve it.

OBJECTIVES

Our analysis of the available treatments in literature discusses the treatment and their safe eliminations. In this study, we give an overview of the measures that could be taken to maintain the elimination gradient of anti-cancer drugs and restore normal kidney function in RCC. Differential therapeutics of RCC/mRCC in various clinical phase trials and the interaction of targeted therapeutics in response to vascular endothelial growth factor (VEGF) were also discussed.

CONCLUSION

Such information might suggest a new direction in controlling treatment with safe elimination through dose adjustment and its associated alternatives in a judicious manner. A strategy to systematically focus on the safe elimination of anti-cancer drugs in RCC strongly needs advocating.

Update on MRI of Cystic Renal Masses Including Bosniak Version 2019

Incidental cystic renal masses are common, usually benign, and almost always indolent. Since 1986, the Bosniak classification has been used to express the risk of malignancy in a cystic renal mass detected at imaging. Historically, magnetic resonance imaging (MRI) was not included in that classification. The proposed Bosniak v.2019 update has formally incorporated MRI, included definitions of imaging terms designed to improve interobserver agreement and specificity for malignancy, and incorporated a variety of masses that were incompletely defined or not included in the original classification. For example, at unenhanced MRI, homogeneous masses markedly hyperintense at T₂ -weighted imaging (similar to cerebrospinal fluid) and homogeneous masses markedly hyperintense at fat suppressed T₁ -weighted imaging (approximately ≥2.5 times more intense than adjacent renal parenchyma) are classified as Bosniak II and may be safely ignored, even when they have not been imaged with a complete renal mass MRI protocol. MRI has specific advantages and is recommended to evaluate masses that at computed tomography (CT) 1) have abundant thick or nodular calcifications; 2) are homogeneous, hyperattenuating, ≥3 cm, and nonenhancing; or 3) are heterogeneous and nonenhancing. Although MRI is generally excellent for characterizing cystic renal masses, there are unique weaknesses of MRI that bear consideration. These details and others related to MRI of cystic renal masses are described in this review, with an emphasis on Bosniak v.2019. A website (https://bosniak-calculator.herokuapp.com/) and mobile phone apps named "Bosniak Calculator" have been developed for ease of assignment of Bosniak classes. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY STAGE: 3.

Comparison of computed tomography and magnetic resonance imaging in the assessment of complex renal cysts by using the Bosniak classification

INTRODUCTION AND OBJECTIVES

The Bosniak classification of cystic renal lesions was first published in 1986 based on computed tomography (CT). In the present study, we aimed to investigate the effect of magnetic resonance imaging (MRI) on Bosniak category compared with CT, and to determine how this effect changed the treatment modality in the evaluation of complex renal cysts.

MATERIAL AND METHODS

Data of 144 patients were collected retrospectively. After exclusion criteria, 102 cystic renal lesions with a Bosniak category of at least IIF on CT or MRI between 2013 and 2016 were evaluated by 2abdominal radiologists. The demographic data, Bosniak category, interobserver agreement, and pathologic data of patients who underwent surgery were recorded.

RESULTS

The coherence between MRI and CT was 75.5%. The Bosniak classification of 17 patients was upgraded with MRI, and the treatment modality changed in 10 patients, and they underwent surgery. The Bosniak category was downgraded from III to IIF in 6 patients out of 8 whose Bosniak category was downgraded with MRI and the treatment modality changed. Surgery was performed in one patient out of these 6 patients, and the pathology was reported as benign. Progression was detected in the follow-up at month 18 of 1 patient out of 5, and surgery was performed. The pathology was reported as renal cell carcinoma. The pathology result was reported as RCC in 35 (68.6%) patients out of 51 who underwent surgery. Progression was detected in 7 patients out of 51 who were followed up (13.7%), and the pathology results were reported as RCC. The majority of the malignant tumors were low stage and grade.

CONCLUSIONS

MRI may be successfully used in the evaluation of renal cystic lesions. In particular, the challenging Bosniak IIF and all Bosniak III lesions must be evaluated using MRI before making the decision for surgery. The upgrading of Bosniak category with MRI is more possible compared with CT due to its high-contrast resolution, therefore further studies are required to identify whether it was the cause of overtreatment of Bosniak III lesions.

Management of complex renal cysts in Canada: results of a survey study

Background

Bosniak III and IV cysts have a high risk of malignancy and have traditionally been managed surgically. However, growing evidence suggests that many can be managed by active surveillance. The main objective of this study was to characterize the use of surveillance in the management of complex renal cysts.

Methods

A web-based survey was sent to all registered, active members of the Canadian Urological Association (N = 583) in October 2018.

Results

The survey response rate was 24.7%. Management of Bosniak III cysts varied considerably. A large proportion of respondents (33.1%) offered active surveillance in > 50% of cases. Only 13.7% of respondents reported never or rarely (< 5% of cases) offering surveillance. In contrast, for Bosniak IV cysts, 60.1% of urologists never or rarely offered surveillance, while only 10.1% offer it in > 50% of cases. A significantly greater proportion of academic urologists, compared to non-academic urologists, viewed surveillance as a management option for patients with a Bosniak III or IV cyst. The most commonly reported barriers to a greater adoption of surveillance were concerns regarding its oncologic safety, the lack of data to support surveillance in this population, and the lack of triggers for discontinuation of active surveillance and intervention.

Conclusions

Despite active surveillance being included as a management option in guidelines, many Canadian urologists are reluctant to offer surveillance to patients with Bosniak III or IV cysts. Practice patterns are heterogeneous among those offering surveillance. High-quality studies are required to better define the benefits and risks of cystic renal mass surveillance.

CT and MR imaging of cystic renal lesions

Cystic renal lesions are a common incidental finding on routinely imaging examinations. Although a benign simple cyst is usually easy to recognize, the same is not true for complex and multifocal cystic renal lesions, whose differential diagnosis includes both neoplastic and non-neoplastic conditions. In this review, we will show a series of cases in order to provide tips to identify benign cysts and differentiate them from malignant ones.

Nonenhancing Component of Clear Cell Renal Cell Carcinoma on Computed Tomography Correlates With Tumor Necrosis and Stage and Serves as a Size-Independent Prognostic Biomarker

OBJECTIVES

This study aimed to quantify nonenhancing tumor (NT) component in clear cell renal cell carcinoma (ccRCC) and assess its association with histologically defined tumor necrosis, stage, and survival outcomes.

METHODS

Among 183 patients with ccRCC, multi-institutional changes in computed tomography attenuation of tumor voxels were used to quantify percent of NT. Associations of NT with histologic tumor necrosis and tumor stage/grade were tested using Wilcoxon signed rank test and with survival outcomes using Kaplan-Meier curves/Cox regression analysis.

RESULTS

Nonenhancing tumor was higher in ccRCC with tumor necrosis (11% vs 7%; P = 0.040) and higher pathological stage (P = 0.042 and P < 0.001, respectively). Patients with greater NT had higher incidence of cancer recurrence after resection (P < 0.001) and cancer-specific mortality (P < 0.001).

CONCLUSION

Nonenhancing tumor on preoperative computed tomographic scans in patients with ccRCC correlates with tumor necrosis and stage and may serve as an independent imaging prognostic biomarker for cancer recurrence and cancer-specific survival.

Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment

Cystic renal cell carcinoma (RCC) is almost certainly overdiagnosed and overtreated. Efforts to diagnose and treat RCC at a curable stage result in many benign neoplasms and indolent cancers being resected without clear benefit. This is especially true for cystic masses, which compared with solid masses are more likely to be benign and, when malignant, less aggressive. For more than 30 years, the Bosniak classification has been used to stratify the risk of malignancy in cystic renal masses. Although it is widely used and still effective, the classification does not formally incorporate masses identified at MRI or US or masses that are incompletely characterized but are highly likely to be benign, and it is affected by interreader variability and variable reported malignancy rates. The Bosniak classification system cannot fully differentiate aggressive from indolent cancers and results in many benign masses being resected. This proposed update to the Bosniak classification addresses some of these shortcomings. The primary modifications incorporate MRI, establish definitions for previously vague imaging terms, and enable a greater proportion of masses to enter lower-risk classes. Although the update will require validation, it aims to expand the number of cystic masses to which the Bosniak classification can be applied while improving its precision and accuracy for the likelihood of cancer in each class.

Active Surveillance of Small (< 4 cm) Bosniak Category 2F, 3, and 4 Renal Lesions: What Happens on Imaging Follow-Up?

OBJECTIVE. The purpose of this study was to determine the percentage of small (< 4 cm) Bosniak category 2F, 3, and 4 lesions that regress during active surveillance. MATERIALS AND METHODS. In this retrospective study, a hospital database was searched from January 1, 2005, through September 9, 2017, for small (< 4 cm) Bosniak category 2F, 3, and 4 lesions studied with initial and follow-up unenhanced and contrast-enhanced CT or MRI. Prospective Bosniak categories were recorded. Two blinded radiologists retrospectively reassigned Bosniak categories to the initial and last follow-up studies. Interreader variability was analyzed. Rates of stability, regression, and progression were calculated and stratified by size. Logistic regression was used to assess the effects of lesion size, lesion growth, and duration of follow-up on the change in Bosniak categories. RESULTS. The search identified 123 patients (85 men, 38 women) with 138 renal lesions (according to the blinded readings, 83 Bosniak category 2F, 37 category 3, and 18 category 4) and followed for 1-12.3 years (median, 2.7 years). Fifty-one percent (70/138) of the lesions were smaller than 2 cm. Eighty-eight percent (73/83) of category 2F lesions were downgraded or remained stable. Forty-five percent (25/55) of category 3 or 4 lesions were downgraded to 2F or lower. Kappa values were 0.94 between the two readers and 0.72-0.76 between the readers and the prospective Bosniak categories. There was no association between initial size, change in size, or duration of follow-up and change in Bosniak category. CONCLUSION. Approximately one-half of small (< 4 cm) Bosniak category 3 and 4 cystic renal lesions were downgraded, and the majority (88%) of small Bosniak category 2F lesions regressed or remained stable during active surveillance. Therefore, small size should be a consideration for conservative management.

Superb microvascular imaging is a rational choice for accurate Bosniak classification of renal cystic masses

OBJECTIVE

Bosniak classification system provides a fine imaging evaluation for the malignant cystic renal masses. Superb microvascular imaging (SMI) is a new ultrasonic technique which apply advanced clutter suppression to reflect microflow information. The aim of this study was to evaluate the performance of ultrasound Bosniak classification aided by SMI in diagnosis of cystic renal masses.

METHODS

By comparing with contrast-enhanced ultrasound (CEUS) and pathology, we evaluated the sensitivity, specificity and accuracy of conventional ultrasound and SMI combination in the diagnosis of renal cystic masses.

RESULTS

Color Doppler Flow image (CDFI) and SMI had significant difference in evaluation the blood flow and Bosniak classification for cystic renal mass of IIf, III and IV (p = 0.020). SMI was consistent with CEUS for cystic renal mass Bosniak classification of IIf, III and IV. Although, CEUS had highest sensitivity of 97.4%, SMI had the highest area under curve in differential diagnosis malignance from benign masses [area under curve = 0.869 (0.743 - 0.995), p < 0.001].

CONCLUSION

SMI can display better in observing blood flow in septa and solid structures of renal cystic lesions compared with CDFI, thus, it can perform more accurate Bosniak classification for renal cystic mass. SMI and CEUS are consistent in Bosniak classification. Bosniak classification aided by SMI maybe an accurate non-invasive ultrasonic examination in distinguishing benign and malignant renal cystic lesions.

ADVANCES IN KNOWLEDGE

Conventional ultrasound had limited ability to distinguish malignance in Bosniak classifications IIf and III. SMI can display better in observing blood flow in septa and solid structures of renal cystic lesions compared with CDFI.

The Complete Spectrum of Infiltrative Renal Masses: Clinical Characteristics and Prognostic Implications

OBJECTIVE

To analyze the full spectrum of patients presenting with radiologically-identified infiltrative renal masses (IRMs), including those managed surgically or otherwise, with focus on clinical presentation/prognosis.

METHODS

All 280 patients presenting with radiologically-identified renal mass with infiltrative features (2008-2017) were retrospectively reviewed. Poorly-defined interface between tumor and parenchyma and irregular shape (nonelliptical) in one or more distinct/unequivocal areas were required for classification as IRM. IRM was confirmed in 265 and clinical characteristics and outcomes were assessed.

RESULTS

Median age/tumor size were 65-years/6.9 cm, respectively, and 225 patients (85%) were R.E.N.A.L. = 10-12. Overall, 181 patients (68%) presented symptomatically, locally-advanced cancer (cT3-T4) was observed in 176 (66%) and disseminated disease and/or lymphadenopathy (>2 cm) in 181(68%). Clinical/radiographic findings were suggestive of etiology and could direct evaluation, but were nonspecific for definitive diagnosis. Renal-mass biopsy was performed in 103 patients and diagnostic in 97 (94%). Renal surgery was only performed in 82 patients (31%) and partial nephrectomy in 3 (1.1%). Overall, 72 patients (27%) received systemic chemotherapy and 59 (22%) targeted therapy. Final-diagnosis was renal cell carcinoma in 94 patients (35%), including 49 with highly-aggressive histology (sarcomatoid/rhabdoid/collecting-duct/medullary/unclassified). High-grade urothelial-carcinoma was found in 70 (26%), and lymphoma/metastatic cancer in 26 (10%)/25 (9%), respectively. Overall, 153 patients (58%) died; 138 (52%) cancer-related at median of 5 months. The majority of patients with renal cell carcinoma, urothelial-carcinoma, and renal metastasis died, almost exclusively cancer-related, at medians of 8, 3, and 2 months, respectively.

CONCLUSION

Our series includes the full spectrum of IRMs and confirms predominance of symptomatic, poorly-differentiated, highly-lethal malignancies. Our study highlights the overriding importance of identifying infiltrative features, a simple radiologic diagnosis, during assessment of renal masses.

Long-term oncological outcomes of cystic renal cell carcinoma according to the Bosniak classification

OBJECTIVES

To evaluate the prognostic role of the Bosniak classification on the long-term oncological outcomes of cystic renal cell carcinomas.

MATERIAL AND METHOD

In a national multicentric retrospective study, we included patients treated surgically for localized cystic RCC from 2000 to 2010. Patients with a follow-up of less than 4 years, benign tumors, and ablative treatments were excluded. The primary outcome was disease-free survival.

RESULTS

152 patients met the inclusion criteria: Bosniak II (6%), III (53%), IV (41%), with a median follow-up of 61 (12-179) months. Characteristics of the population and the tumors were [median, (min-max)] age 57 (25-84) years old, tumor size 43 mm (20-280), RENAL score 7 (4-12), PADUA score 8 (5-14). Treatments were 55% partial nephrectomy, 45% radical nephrectomy, 74% open surgery, and 26% laparoscopy. In pathological report, cystic RCC were mainly of low grade (1-2, 77%) and low stage (pT1, 81%). The two main histological subtypes were conventional (56%) and papillary (23%) RCC. Staging at presentation and histological characteristics were similar between Bosniak III and IV, except for high grade which was more common in Bosniak IV (12 vs 36%, p < 0.01). The Bosniak classification was not predictive of the recurrence, as 5- and 10-year disease-free survival were similar in Bosniak III and IV (92% vs 92% and 84% vs 83%, p = 0.60).

CONCLUSION

The Bosniak classification is predictive of the risk of malignancy but not of the oncological prognosis. Regardless of the initial Bosniak categories, almost all cystic RCCs were of low stage/grade and had low long-term recurrence rate.

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.

Contemporary update on imaging of cystic renal masses with histopathological correlation and emphasis on patient management

This article presents an updated review of cystic renal mass imaging. Most cystic renal masses encountered incidentally are benign and can be diagnosed confidently on imaging and require no follow-up. Hyperattenuating masses discovered at unenhanced or single-phase enhanced computed tomography (CT) measuring between 20-70 HU are indeterminate and can be further investigated first by using ultrasound and, then with multi-phase CT or magnetic resonance imaging (MRI); as the majority represent haemorrhagic/proteinaceous cysts (HPCs). Dual-energy CT may improve differentiation between HPCs and masses by suppressing unwanted pseudo-enhancement observed with conventional CT. HPCs can be diagnosed confidently when measuring >70 HU at unenhanced CT or showing markedly increased signal on T1-weighted imaging. Although the Bosniak criteria remains the reference standard for diagnosis and classification of cystic renal masses, histopathological classification and current management has evolved: multilocular cystic renal cell carcinoma (RCC) has been reclassified as a cystic renal neoplasm of low malignant potential, few Bosniak 2F cystic masses progress radiologically during follow-up; RCC with predominantly cystic components are less aggressive than solid RCC; and Bosniak III cystic masses behave non-aggressively. These advances have led to an increase in non-radical management or surveillance of cystic renal masses including Bosniak 3 lesions. Tubulocystic RCC is a newly described entity with distinct imaging characteristics, resembling a pancreatic serous microcystadenoma. Other benign cystic masses including: mixed epithelial stromal tumours (MEST) are now considered in the spectrum of cystic nephroma and angiomyolipoma (AML) with epithelial cysts (AMLEC) resemble a fat-poor AML with cystic components.

Cystic Renal Cell Carcinoma: A Report on Outcomes of Surgery and Active Surveillance in Patients Retrospectively Identified on Pretreatment Imaging

PURPOSE

We evaluated the outcomes of surgical intervention and active surveillance in patients diagnosed with cystic renal cell carcinoma at our hypothesized radiological cutoff of greater than 50% cystic.

MATERIALS AND METHODS

We identified all 430 patients with a pathologically confirmed cystic renal mass that fit our criteria from 2000 to 2015. The 292 patients with a lack of computerized tomography, tumors less than 50% cystic on imaging, multifocal tumors and prior renal cell carcinoma were excluded from study. Patients were stratified into benign or malignant subgroups, and radiological, clinicopathological and oncologic features were determined. Univariate and multivariate associations between clinicoradiological parameters in each group were analyzed. We similarly reviewed the records of a separate cohort of patients treated with active surveillance for cystic renal cell carcinoma.

RESULTS

Of the 138 identified cases of cystic renal cell carcinoma 102 (73.9%) were renal cell carcinoma and 36 (26.1%) were benign masses. Of the tumors 77.5% were Fuhrman grade 1-2, 83.4% were stage pT2 or less and 65.9% showed clear cell histology. On univariate analysis male gender, a solid component and increasing Bosniak classification were significant for malignancy. In a separate cohort we identified 38 patients on active surveillance. The growth rate was 1.0 mm per year overall and 2.3 mm per year for the solid component. At a median followup of more than 4 years in all cohorts there was no evidence of recurrence or metastasis of cystic renal cell carcinoma.

CONCLUSIONS

Patients with unifocal cystic renal cell carcinoma evaluated using a standardized radiological threshold of greater than 50% cystic had an excellent prognosis on active surveillance and after surgical resection.

Imaging and Screening of Kidney Cancer

Renal cell carcinoma (RCC) exhibits a diverse and heterogeneous disease spectrum, but insight into its molecular biology has provided an improved understanding of potential risk factors, oncologic behavior, and imaging features. Computed tomography (CT) and MR imaging may allow the identification and preoperative subtyping of RCC and assessment of a response to various therapies. Active surveillance is a viable management option in some patients and has provided further insight into the natural history of RCC, including the favorable prognosis of cystic neoplasms. This article reviews CT and MR imaging in RCC and the role of screening in selected high-risk populations.

Differences in Renal Tumor Size Measurements for Computed Tomography Versus Magnetic Resonance Imaging: Implications for Patients on Active Surveillance

PURPOSE

To evaluate and compare the accuracy of computed tomography (CT) and magnetic resonance imaging (MRI) in predicting the final pathologic tumor size of partial nephrectomy specimens.

MATERIALS AND METHODS

We analyzed a multi-institutional database of 807 patients who underwent robotic partial nephrectomy for a cT1a renal mass from 2006 to 2016. Patients who had a solitary tumor with complete data on the baseline imaging modality and the tumor size (baseline and pathologic) (n = 349) were included for analysis. Baseline tumor size evaluated by both imaging modalities, in addition to the difference between the measurements and final pathologic tumor size (cm) measurements, was compared between patients who received a baseline CT (n = 276, 79.1%) and those who received an MRI (n = 73, 20.9%).

RESULTS

There were no statistically significant differences between any baseline characteristics and receipt of a CT versus MRI. In multivariable analysis adjusting for confounders, there was no significant difference in the baseline tumor size between patients receiving an MRI and those receiving a CT (2.3 versus 2.6 cm; β = -0.13; 95% confidence interval [CI] = -0.33 to 0.07; P = .208). Tumor size on imaging was smaller from final pathology by 0.43 cm on average (P = .002). Measurement error for the measured baseline versus actual pathologic tumor size did not significantly differ for patients receiving an MRI versus those receiving a CT (0.38 versus 0.44 cm; β = -0.06; 95% CI = -0.16 to 0.04; P = .232).

CONCLUSION

Baseline renal tumor size measurements were not significantly different for CT scan and MRI. Choice of imaging modality can be based on doctor and patient preference, including cost and exposure to radiation.

Adult Renal Cell Carcinoma: A Review of Established Entities from Morphology to Molecular Genetics

According to the current World Health Organization (WHO), renal cell carcinomas (RCCs) that primarily affect adults are classified into 8 major subtypes. Additional emerging entities in renal neoplasia have also been recently recognized and these are discussed in further detail by Mehra et al (Emerging Entities in Renal Neoplasia, Surgical Pathology Clinics, 2015, Volume 8, Issue 4). In most cases, the diagnosis of a RCC subtype can be based on morphologic criteria, but in some circumstances the use of ancillary studies can aid in the diagnosis. This review discusses the morphologic, genetic, and molecular findings in RCCs previously recognized by the WHO, and provides clues to distinction from each other and some of the newer subtypes of RCC. As prognosis and therapeutic options vary for the different subtypes of RCC, accurate pathologic distinction is critical for patient care.

Cystic renal masses

PURPOSE

The purpose of the study is to provide an update on the imaging evaluation of cystic renal masses, to review benign and malignant etiologies of cystic renal masses, and to review current controversies and future directions in the management of these lesions.

CONCLUSIONS

Cystic renal masses are relatively common in daily practice. The Bosniak classification is a time-proven method for the imaging classification and management of these lesions. Knowledge of the pathognomonic features of certain benign Bosniak 2F/3 lesions is important to avoid surgery on these lesions (e.g., localized cystic disease, renal abscess). For traditionally surgical Bosniak lesions (Classes 3 and 4), there are evolving data that risk stratification based on patient demographics, imaging size, and appearance may allow for expanded management options including tailored surveillance or ablation, along with the traditional surgical approach.