Multilocular Cystic Renal Cell Carcinoma: Pathological T Staging Makes No Difference to Favorable Outcomes and Should be Reclassified

Contrast-Enhanced Ultrasound of the Indeterminate Renal Mass, From the AJR "How We Do It" Special Series

Contrast-enhanced ultrasound (CEUS) is distinguished from CT and MRI by the use of microbubble ultrasound contrast agents (UCAs) with intravascular blood pool distribution. When performing CEUS, low-intensity ultrasound allows real-time tissue subtraction imaging, whereas high-intensity ultrasound leads to microbubble destruction, enabling visualization of the contrast inflow pattern. CEUS has exceptional contrast resolution that enables the detection of even minimal blood flow, achieving very high NPV for ruling out vascular perfusion and providing high frame rates in the evaluation of tissue perfusion dynamics. UCAs undergo hepatic metabolism and pulmonary clearance, ensuring safety in patients with renal impairment. CEUS excels in distinguishing solid from cystic renal masses, with higher sensitivity than CT or MRI for detection of lesion enhancement. CEUS can aid the further characterization of both solid and cystic lesions and may have particular applications in the surveillance of cystic masses and surveillance after renal cell carcinoma ablation. This review describes the use of CEUS to help characterize indeterminate renal masses, based on the authors' institutional experience. The article highlights key differences between CEUS and CT or MRI, and provides practical insights for performing and interpreting CEUS of renal masses.

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.

Comparison of survival between unilocular cystic and purely solid renal cell carcinoma

To evaluate clinicopathological features and survival outcomes of unilocular cystic renal cell carcinoma (ucRCC) compared with purely solid renal cell carcinoma (sRCC), and to evaluate the oncologic aggressiveness of ucRCC. The relevant data of 957 patients with sporadic unilateral renal cell carcinoma (RCC) underwent surgical treatment in 2 institutions from Jan 2014 to Oct 2018 were obtained. We excluded multilocular cystic renal neoplasm of low malignant potential (MCRNLMP), RCC with multilocular cysts and necrotic RCC. 74 ucRCCs were identified by pathology reports. We performed propensity score matching (PSM) and eventually selected 144 sRCCs. The clinicopathological features and survival outcomes were compared properly. After PSM, age, BMI, Charlson Comorbidity Index, and postoperative Chronic Kidney Disease grade were not significantly different. Both overall survival and progression-free survival of ucRCC were significantly better than sRCC by the log-rank test. Twenty-five cases of sRCCs were in the pT3 or pT4 stage, while no pT3 or pT4 tumors were found in ucRCCs. Fuhrman grade and lymphatic metastasis were found to be significant prognostic factors for the overall survival of ucRCC. Unilocular cystic RCC has a lower Fuhrman grade and pathological stage and a better prognosis compared with solid RCC. Patients with ucRCC still probably have lymphatic metastasis at surgery and may have postoperative metastasis, which is different from MCRNLMP. We recommend that the diagnosis of ucRCC should be reflected in pathology report. Different subtype of cystic RCC should be taken into consideration in counseling and management.

A Comprehensive Commentary on the Multilocular Cystic Renal Neoplasm of Low Malignant Potential: A Urologist’s Perspective

Multilocular cystic renal neoplasm of low malignant potential (MCRNLMP) is a cystic renal tumor with indolent clinical behavior. In most of cases, it is an incidental finding during the examination of other health issues. The true incidence rate is estimated to be between 1.5% and 4% of all RCCs. These lesions are classified according to the Bosniak classification as Bosniak category III. There is a wide spectrum of diagnostic tools that can be utilized in the identification of this tumor, such as computed tomography (CT), magnetic resonance (MRI) or contrast-enhanced ultrasonography (CEUS). Management choices of these lesions range from conservative approaches, such as clinical follow-up, to surgery. Minimally invasive techniques (i.e., robotic surgery and laparoscopy) are preferred, with an emphasis on nephron sparing surgery, if clinically feasible.

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.

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.

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.

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.

Roles for active surveillance in renal cancer

PURPOSE OF REVIEW

With this review, we describe the most recent advances in active surveillance as well as diagnosis and management of small renal masses (SRMs).

RECENT FINDINGS

We discuss diagnosis, differentiation of solid from cystic lesions, risk prediction and treatment of the SRM. A better understanding of the disease facilitates the use of more conservatory treatments, such as active surveillance. Active surveillance has been increasingly accepted not only for SRM, but also for larger tumors and even metastatic patients. Exiting advances in risk prediction will help us define which patients can be safely managed with active surveillance and which require immediate treatment. Meanwhile, the use of renal tumor biopsies is still an important tool for these cases.

SUMMARY

Active surveillance is an option for many patients with renal masses. Noninvasive methods for diagnosis and risk prediction are being developed, but meanwhile, renal tumor biopsy is a useful tool. A better understanding of the disease increases the number of patients who can undergo active surveillance fully certain of the safety of their management.

Imaging of Unusual Renal Tumors

PURPOSE OF REVIEW

Renal masses are a wide entity and a common finding in clinical practice. Detection of these masses has increased in the last years, yet mortality rates have slightly decreased.

RECENT FINDINGS

According to the World Health Organization classification, there are 8 types, 51 subtypes, and a lot more subsequent subclassifications of renal tumors. Histopathological analysis should always be assessed for final diagnosis of theses tumors. However, imaging can be an important diagnostic guidance. The most common diagnoses of renal tumor are clear cell carcinoma, papillary renal cell carcinoma, angiomyolipoma, and transitional cell carcinoma. Nonetheless, a considerable variety of particular tumors can arise from the kidney, challenging the expertise of radiologists and urologists on this subject. The awareness of these unusual entities is vital for professionals working at a complex medical facility with greater volume of patients. We hereby present uncommon renal tumors and its pathological and radiological features.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.