Query: Bosniak

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

title: MRI based Bosniak Classification of Cystic Renal Masses, Version 2019: Interobserver Agreement, Impact of Readers' Experience, and Diagnostic Performance.
abstract: The 2019 Bosniak classification (version 2019) of cystic renal masses (CRMs) provides a systematic update to the currently used 2005 Bosniak classification (version 2005) Further validation is required before widespread application.  To evaluate the interobserver agreement of MRI criteria, the impact of readers' experience, and the diagnostic performance between version 2019 and version 2005.  From January 2009 to December 2018, consecutive patients with CRM who had undergone renal MRI and surgical pathologic examination were included in this retrospective study. On the basis of version 2019 and version 2005, all CRMs were independently classified by eight radiologists with different levels of experience. By using multirater k statistics, interobserver agreement was evaluated with comparisons between classifications and between senior and junior radiologists. Diagnostic performance between classifications by dichotomizing classes I IV into lower (I IIF) and higher (III IV) classes was compared by using the McNemar test. P .05 was considered to indicate a statistically significant difference.  A total of 207 patients (mean age standard deviation, 49 years 12; 139 male and 68 female patients) with CRMs were included. Overall, interobserver agreement was higher with version 2019 than version 2005 (weighted k 0.64 vs 0.50, respectively; P .001) Interobserver agreement between senior and junior radiologists did not differ between version 2019 (weighted k 0.65 vs 0.64, respectively; P .71) and version 2005 (weighted k 0.54 vs 0.46; P .001) Diagnostic specificity for malignancy was higher with version 2019 than with version 2005 (83% [92 of 111] vs 68% [75 of 111] respectively; P .001) without any difference in sensitivity (89% [85 of 96] vs 84% [81 of 96] P .34)  In the updated Bosniak classification, interobserver agreement improved and was unaffected by observers' experience. The diagnostic performance with version 2019 was superior to that with version 2005, with higher specificity. Published under a CC BY 4.0 license. Online supplemental material is available for this article. See also the editorial by Choyke in this issue.

title: Bosniak Classification Version 2019 of Cystic Renal Masses Assessed With MRI.
abstract: The purpose of this study was to determine how use of Bosniak classification version 2019 affects categorization and overall accuracy of MRI evaluation of cystic renal masses with tissue pathologic analysis as the reference standard.  MR images of 50 consecutively registered patients with tissue pathologic results from 2005 to 2019 were retrospectively reviewed by two abdominal radiologists. Each radiologist independently assigned a category based on the original and Bosniak classification version 2019 systems. Interreader agreements (kappa statistic) for both were calculated, and consensus reading was performed. Tissue pathologic analysis was used as the reference standard to determine whether a lesion was benign or renal cell carcinoma.  Fifty nine cystic renal masses were characterized as 38 renal cell carcinomas and 21 benign lesions on the basis of the results of tissue pathologic analysis. By consensus, according to the original Bosniak criteria, the renal masses were classified into three category I, five category II, four category IIF, 25 category III, and 22 category IV lesions. By consensus, according to the version 2019 criteria, the renal masses were classified into three category I, two category II, 12 category IIF, 18 category III, and 24 category IV lesions. Overall sensitivity and specificity for identifying renal cell carcinoma were 95% and 81% respectively, with the original classification system and 100% and 86% respectively, with version 2019. Weighted interreader agreement was moderate for both the original system (k 0.57) and version 2019 (k 0.55) CONCLUSION. Use of Bosniak classification version 2019 system improves sensitivity and specificity for malignancy among cystic renal masses characterized with MRI. Most lesions that changed categories were reclassified as Bosniak category IIF.

title: Bosniak Classification of Cystic Renal Masses Version 2019: Comparison of Categorization using CT and MRI.
abstract: Please see the Author Video associated with this article.  Bosniak Classification, version 2019 recently proposed refinements for cystic renal mass characterization and now formally incorporates MRI, which may improve concordance with CT.  To compare concordance of CT and MRI in evaluation of cystic renal masses using Bosniak Classification, version 2019.  In this IRB approved and HIPAA compliant study, three abdominal radiologists (R1 R3) retrospectively reviewed 68 consecutive cystic renal masses from 45 patients assessed with both CT and MR renal mass protocols within a year between 2005 2019. CT and MRI were reviewed independently and in separate sessions, using both the original and version 2019 Bosniak Classification systems.  Using Bosniak Classification, version 2019, cystic renal masses were classified into 12 category I, 19 category II, 13 category IIF, 4 category III, and 20 category IV by CT and 8 category I, 15 category II, 23 category IIF, 9 category III, and 13 category IV by MRI. Among individual features, MRI depicted more septa (p<0.001, p=0.046, p=0.005 for R1 R3; McNemar's test) for all radiologists, though both CT and MRI showed a similar number of protrusions (p=0.823, 1.0, 0.302) and maximal septa/wall thickness (p=1.0, 1.0, 0.145) Of discordant cases with version 2019, MRI led to the higher category in 12 masses. Reason for upgrade was most commonly due to protrusions identified only on MRI (n=4) increased number of septa (n=3) and a new category of heterogeneously T1 hyperintense (n=3) Neither modality was more likely to lead to a category change for both version 2019 (p=0.502; McNemar's test) and the original Bosniak classification system (p=0.823) Overall inter rater agreement was substantial for both CT (k=0.745) and MRI (k=0.655) using version 2019 and was slightly higher than that of the original system (CT k=0.707; MRI k=0.623)  CT and MRI were concordant in the majority of cases using Bosniak Classification, version 2019 and category changes by modality were not statistically significant. Inter rater agreements were substantial for both CT and MRI.  2019 applied to cystic renal masses has substantial inter rater agreement and does not lead to systematic category upgrades with either CT or MRI.

title: EFSUMB 2020 Proposal for a Contrast Enhanced Ultrasound Adapted Bosniak Cyst Categorization Position Statement.
abstract: The well established Bosniak renal cyst classification is based on contrast enhanced computed tomography determining the malignant potential of cystic renal lesions. Ultrasound has not been incorporated into this pathway. However, the development of ultrasound contrast agents coupled with the superior resolution of ultrasound makes it possible to redefine the imaging of cystic renal lesions. In this position statement, an EFSUMB Expert Task Force reviews, analyzes, and describes the accumulated knowledge and limitations and presents the current position on the use of ultrasound contrast agents in the evaluation of cystic renal lesions.

title: Prevalence of Malignancy and Histopathologic Association of Bosniak Classification, Version 2019 Class III and IV Cystic Renal Masses.
abstract: version 2019 (v2019) describes two types of class III and IV masses each: 1) thick, wall/septa =4 mm (III WS) 2) obtuse protrusion =3 mm (III OP) 3) obtuse protrusion =4 mm (IV OP) and 4) acute protrusion of any size (IV AP) The purposes were to determine the prevalence of malignancy and histopathologic features of class III and IV masses and subclasses.  In this IRB approved and HIPAA compliant study, three fellowship trained abdominal radiologists (R1 3) reviewed cystic renal masses that had tissue pathology and pre operative renal mass protocol CT or MRI. Classes based on v2019 and prior classification systems were retrospectively re assigned and associated with malignancy, aggressive histologic features (necrosis or high Fuhrman grade) and radiologic progression following resection.  The final sample included 79 masses (59 malignant, 20 benign) from 74 patients. Based on v2019, prevalence of malignancy ranged from 56 61% (mean 60% for class III and 83 83% (mean 83% for class IV (p=0.036, 0.013, 0.036 for R1 3) Prevalence of malignancy within subclasses were: III WS (47 53% III OP (71 85% IV OP (75 87% IV AP (87 95% p=0.029, 0.001, 0.005) All readers were more likely to classify malignancies with aggressive histologic features as class IV (88 100% rather than class III (0 12% p=0.012, <0.001, 0.002) corresponding to a negative predictive value of 96 100% Following treatment (mean follow up length 1210 days) one patient developed metastases.  2019 can help risk stratification of class III IV masses by identifying those likely to be malignant and have aggressive histologic features.

title: Stratification of cystic renal masses into benign and potentially malignant: applying machine learning to the bosniak classification
abstract: To create a CT texture based machine learning algorithm that distinguishes benign from potentially malignant cystic renal masses as defined by the Bosniak Classification version 2019.  In this IRB approved, HIPAA compliant study, 4,454 adult patients underwent renal mass protocol CT or CT urography from January 2011 to June 2018. Of these, 257 cystic renal masses were included in the final study cohort. Each mass was independently classified using Bosniak version 2019 by three radiologists, resulting in 185 benign (Bosniak I or II) and 72 potentially malignant (Bosniak IIF, III or IV) masses. Six texture features: mean, standard deviation, mean of positive pixels, entropy, skewness, kurtosis were extracted using commercial software TexRAD (Feedback PLC, Cambridge, UK) Random forest (RF) logistic regression (LR) and support vector machine (SVM) machine learning algorithms were implemented to classify cystic renal masses into the two groups and tested with tenfold cross validations.  Higher mean, standard deviation, mean of positive pixels, entropy, skewness were statistically associated with the potentially malignant group P 0.0015 each) Sensitivity, specificity, positive predictive value, negative predictive value, and area under curve of RF model was 0.67, 0.91, 0.75, 0.88, 0.88; of LR model was 0.63, 0.93, 0.78, 0.86, 0.90, and of SVM model was 0.56, 0.91, 0.71, 0.84, 0.89, respectively.  Three CT texture based machine learning algorithms demonstrated high discriminatory capability in distinguishing benign from potentially malignant cystic renal masses as defined by the Bosniak Classification version 2019. If validated, CT texture based machine learning algorithms may help reduce interreader variability when applying the Bosniak classification.

title: Bosniak classification of cystic renal masses version 2019 does not increase the interobserver agreement or the proportion of masses categorized into lower Bosniak classes for non subspecialized readers on CT or MR.
abstract: In a condition so prevalent as renal cysts, classifications should display satisfactory reproducibility not only among subspecialized readers. We aimed to compare the interobserver agreement of the Bosniak classification version 2019 (BC19) and current Bosniak classification (CBC) for non subspecialized readers on CT and MRI and to verify whether BC19 leads to a downgrade of renal cystic masses when compared to CBC.  We evaluated 50 renal cystic masses in 47 patients on MR and CT (25 per method) Eighteen readers (nine third year radiology residents and nine abdominal imaging fellows) assessed the images using BC19 and CBC with an eight week interval. Kappa statistic was used to assess agreement. An average score of Bosniak categories across all raters evaluated if there was downgrading of lesions on BC19.  The highest values of Kappa were found for fellows on CBC MR (k 0.51) and the lowest values were found for residents on CBC MR and fellows on BC19 MR (both k 0.36) On CBC, interobserver agreement was moderate for MR and CT (k 0.42 and 0.43, respectively) whereas on BC19, it was fair (k 0.38 and 0.40, respectively) The best agreements were in categories I (k 0.49 0.69) and IV (k 0.45 0.51) The poorest agreements occurred at IIF (k 0.18 on BC19 CT) There was a moderate median increase from CBC to BC19 in terms of Bosniak categories for both methods (MR [Z= 2.058, p 0.040] and CT [Z= 2.509, p 0.012] CONCLUSION BC19, when compared to CBC, did not improve interobserver agreement nor diminished the proportion of masses categorized into lower Bosniak classes among non subspecialized readers.

title: Contrast Enhanced Ultrasound (CEUS) for the Evaluation of Bosniak III Complex Renal Cystic Lesions A 10 Year Specialized European Single Center Experience with Histopathological Validation
abstract: The aim of the present retrospective single center study is to evaluate the diagnostic performance of contrast enhanced ultrasound (CEUS) for assessing Bosniak III complex renal cystic lesions with histopathological validation.  49 patients with CEUS categorized Bosniak III renal cystic lesions were included in this retrospective study. All patients underwent native B mode, Color Doppler, contrast enhanced ultrasound (CEUS) between 2010 2020. Eight and five patients underwent computed tomography (CT) and magnetic resonance imaging (MRI) respectively. Twenty nine underwent (partial) nephrectomy allowing for histopathological analysis. The applied contrast agent for CEUS was a second generation blood pool agent. Ultrasonography examinations were performed and interpreted by a single experienced radiologist with more than 15 years of experience (EFSUMB Level 3)  CEUS examinations were successfully performed in all included patients without registering any adverse effects. The malignancy rate of CEUS categorized Bosniak III renal lesions accounted for 66% Initially, cystic complexity was visualized in native B mode. In none of the renal lesions hypervascularization was detected in Color Doppler. CEUS allowed for detection of contrast enhancement patterns in all included Bosniak III renal lesions. Delayed wash out could be detected in 6/29 renal lesions. In two cases of histopathologically confirmed clear cell RCC, appropriate up grading from Bosniak IIF to III was achieved by CEUS.  CEUS depicts a promising imaging modality for the precise diagnostic workup and stratification of renal cystic lesions according to the Bosniak classification system, thereby helping guidance of adequate clinical management in the future.

title: Update on MRI of Cystic Renal Masses Including Bosniak Version 2019
abstract: 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.