The Histopathologic Correlation of Bosniak 3 Cyst Subclassification

The efficacy of the new Bosniak classification v.2019 in benign lesions prediction within the higher Bosniak cysts classes

INTRODUCTION

Identification of benign lesions among higher classes of renal Bosniak cysts who are vulnerable to active surveillance instead of surgical approach is still questionable. We aimed in this study to delineate the efficacy of the new Bosniak v2019 classification in benign lesions identification among those cases with higher Bosniak classes in comparison with the final histopathology.

MATERIALS

In a retrospective review between 2010 and 2021 for patients diagnosed as higher classes Bosniak renal masses was done. Patients' demographics and radiological data i.e.,: age, gender, and final Bosniak v2019 categorization for class III: (1) Enhancing thick wall/septa >4 mm (III-WS) and (2) Enhancing irregular wall/septa or convex protrusion with obtuse margins <3 mm (III-OP) and for class IV as: (1) Enhancing nodule or convex protrusion with obtuse margins >4 mm (IV-OP) and (2) Enhancing nodule or convex protrusion with acute margins of any size (IV-AP).

RESULTS

A total of 137 patients were included. Bosniak III was identified in 56 patients. Malignancy was detected in 74.5% of resected masses. Among resected Bosniak III cyst, 46.4% were benign histopathologically. Male gender and Bosniak III-OP were independent risks for malignancy among the resected Bosniak III cysts. Conversely, in resected Bosniak IV renal cysts, only 9 of resected masses were benign. In univariate analysis, male gender, absence of multilocular cyst and endophytic masses were predictors for malignancy in resected Bosniak IV cyst. None of the previous predictors was significant in multivariate analysis.

CONCLUSION

The Bosniak subclassification v.2019 can define benign lesions. Bosniak III-OP was an independent risk for malignancy detection among the resected Bosniak III cysts.

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.

Pilot Study for the Assessment of the Best Radiomic Features for Bosniak Cyst Classification Using Phantom and Radiologist Inter-Observer Selection

Since the Bosniak cysts classification is highly reader-dependent, automated tools based on radiomics could help in the diagnosis of the lesion. This study is an initial step in the search for radiomic features that may be good classifiers of benign-malignant Bosniak cysts in machine learning models. A CCR phantom was used through five CT scanners. Registration was performed with ARIA software, while Quibim Precision was used for feature extraction. R software was used for the statistical analysis. Robust radiomic features based on repeatability and reproducibility criteria were chosen. Excellent correlation criteria between different radiologists during lesion segmentation were imposed. With the selected features, their classification ability in benignity-malignity terms was assessed. From the phantom study, 25.3% of the features were robust. For the study of inter-observer correlation (ICC) in the segmentation of cystic masses, 82 subjects were prospectively selected, finding 48.4% of the features as excellent regarding concordance. Comparing both datasets, 12 features were established as repeatable, reproducible, and useful for the classification of Bosniak cysts and could serve as initial candidates for the elaboration of a classification model. With those features, the Linear Discriminant Analysis model classified the Bosniak cysts in terms of benignity or malignancy with 88.2% accuracy.

Proportion of malignancy in Bosniak classification of cystic renal masses version 2019 (v2019) classes: systematic review and meta-analysis

OBJECTIVES

Determine the proportion of malignancy within Bosniak v2019 classes.

METHODS

MEDLINE and EMBASE were searched. Eligible studies contained patients with cystic renal masses undergoing CT or MRI renal protocol examinations with pathology confirmation, applying Bosniak v2019. Proportion of malignancy was estimated within Bosniak v2019 class. Risk of bias was assessed using QUADAS-2.

RESULTS

We included 471 patients with 480 cystic renal masses. No class I malignant masses were observed. Pooled proportion of malignancy were class II, 12% (6/51, 95% CI 5-24%); class IIF, 46% (37/85, 95% CI 28-66%); class III, 79% (138/173, 95% CI 68-88%); and class IV, 84% (114/135, 95% CI 77-90%). Proportion of malignancy differed between Bosniak v2019 II-IV classes (p = 0.004). Four studies reported the proportion of malignancy by wall/septa feature. The pooled proportion of malignancy with 95% CI were class III thick smooth wall/septa, 77% (41/56, 95% CI 53-91%); class III obtuse protrusion ≤ 3 mm (irregularity), 83% (97/117, 95% CI 75-89%); and class IV nodule with acute angulation, 86% (50/58, 95% CI 75-93%) or obtuse angulation ≥ 4 mm, 83%, (64/77, 95% CI 73-90%). Subgroup analysis by wall/septa feature was limited by sample size; however, no differences were found comparing class III masses with irregularity to class IV masses (p = 0.74) or between class IV masses by acute versus obtuse angles (p = 0.62).

CONCLUSION

Preliminary data suggest Bosniak v2019 class IIF masses have higher proportion of malignancy compared to the original classification, controlling for pathologic reference standard. There are no differences in proportion of malignancy comparing class III masses with irregularities to class IV masses with acute or obtuse nodules.

KEY POINTS

• The proportion of malignancy in Bosniak v2019 class IIF cystic masses is 46% (37 malignant/85 total IIF masses, 95% confidence intervals (CI) 28-66%). • The proportion of malignancy in Bosniak v2019 class III cystic masses is 79% (138/173, 95% CI 68-88%) and in Bosniak v2019 class IV cystic masses is 84% (114/135, 95% CI 77-90%). • Class III cystic masses with irregularities had similar proportion of malignancy (83%, 97/117, 95% CI 75-89%) compared to Bosniak class IV masses (84%, 114/135, 95% CI 77-90%) overall (p = 0.74) with no difference within class IV masses by acute versus obtuse angulation (p = 0.62).

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.

Predictive Value of Additional Clinical and Radiological Parameters for Discrimination of Malignancy in Bosniak 3 Cysts

INTRODUCTION

Almost half of the cystic renal lesions are still overdiagnosed and overtreated. New clinical and radiological parameters are needed to distinguish the malignant Bosniak 3 lesions from the benign ones. We aimed to evaluate the clinical and radiological parameters that may be related to malignancy risk for Bosniak category 3 renal cysts.

MATERIALS AND METHODS

Patients who underwent surgical resection of a histopathologically confirmed Bosniak 3 renal cyst between March 2007 and September 2019 were evaluated. Two experienced uro-radiologists have reevaluated the last preoperative computed tomography and/or MRI images of the patients and reclassified the lesions according to the Bosniak classification. They also reported cystic features such as nodularity, septation, focal thickening, enhancement, and calcification. Clinical, pathological, and oncological outcomes were recorded. Then patients were divided into 2 groups as Group 1 (benign pathology) and Group 2 (malignant pathology) according to final histopathological report.

RESULTS

A total of 79 patients were included in this study. Mean follow-up time was 47 ± 34 months. There were 30 patients in Group 1 and 49 patients in Group 2. Hypertension (p = 0.001) and smoking history (p = 0.008) were more common in malignant group. Among the radiological findings, lower tumor diameter (p = 0.024), presence of cyst wall enhancement (p = 0.025), presence of nodularity (p = 0.002), and presence of focal thickening (p = 0.031) were found to be statistically significant for malignancy. Most of the tumors were at pathological T1 stage and Fuhrmann Grade 1-2. Only nodularity was found to be independent predictive factor for malignancy in multivariate analysis.

CONCLUSION

Clinical factors including hypertension and smoking, radiological factors including lower lesion size, cyst wall enhancement, nodularity, and focal thickening were predictors for malignancy of Bosniak 3 cysts.