Bosniak Classification for Complex Renal Cysts Reevaluated: A Systematic Review
Abstract
Purpose:
We systematically evaluated the Bosniak classification system with malignancy rates of each Bosniak category, and assessed the effectiveness related to surgical treatment and oncologic outcome based on recurrence and/or metastasis.
Materials and Methods:
In a systematic review according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement and the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies) criteria, we selected 39 publications for inclusion in this analysis and categorized them into 1) surgical cohorts—all cysts treated surgically and 2) radiological cohorts—cysts with surgical treatment or radiological followup.
Results:
A total of 3,036 complex renal cysts were categorized into Bosniak II, IIF, III and IV. In surgical and radiological cohorts pooled estimates showed a malignancy prevalence of 0.51 (0.44, 0.58) in Bosniak III and 0.89 (0.83, 0.92) in Bosniak IV cysts, respectively. Stable Bosniak IIF cysts showed a malignancy rate of less than 1% during radiological followup (surveillance). Bosniak IIF cysts, which showed reclassification to the Bosniak III/IV category during radiological followup (12%), showed malignancy in 85%, comparable to Bosniak IV cysts. The estimated surgical number needed to treat to avoid metastatic disease of Bosniak III and IV cysts was 140 and 40, respectively.
Conclusions:
The effectiveness of the Bosniak classification system for complex renal cysts was high in categories II, IIF and IV, but low in category III, and 49% of Bosniak III cysts was overtreated because of a benign outcome. This surgical overtreatment combined with the excellent outcome for Bosniak III cysts may suggest that surveillance is a rational alternative to surgery. This will require further study to assess whether surveillance of Bosniak III cysts will prove safe.
References
- 1 : Calcification in cystic renal masses: is it important in diagnosis?. Radiology2003; 226: 47. Google Scholar
- 2 : Cystic renal masses: usefulness of the Bosniak classification. Urol Radiol1991; 13: 83. Google Scholar
- 3 : Laparoscopic evaluation of indeterminate renal cysts. Urology1995; 45: 1066. Google Scholar
- 4 : Surgical management of complex renal cysts: a series of 32 cases. J Urol1996; 156: 28. Link, Google Scholar
- 5 : CT of cystic renal masses: analysis of diagnostic performance and interobserver variation. AJR Am J Roentgenol1997; 169: 813. Google Scholar
- 6 : Complex renal cysts: findings on MR imaging. AJR Am J Roentgenol1999; 172: 1495. Google Scholar
- 7 : The preoperative diagnosis of complex renal cystic masses. Arch Esp Urol1999; 52: 19. Google Scholar
- 8 : Cystic renal masses: accurate Bosniak classification requires adequate renal CT. AJR Am J Roentgenol2000; 175: 339. Google Scholar
- 9 : An evaluation of Bosniak's radiological classification of cystic renal masses. BJU Int2000; 86: 607. Google Scholar
- 10 : Laparoscopic evaluation of indeterminate renal cysts. Long-term follow-up. J Endourol2002; 16: 79. Google Scholar
- 11 : Laparoscopic partial nephrectomy for cystic masses. J Urol2005; 174: 614. Link, Google Scholar
- 12 : Atypical cysts and risk of renal cancer: value and danger of the Bosniak classification. Prog Urol2006; 16: 292. Google Scholar
- 13 : Diagnosis and laparoscopic treatment of renal cysts of Bosniak type III and IV. Urologiia2008; 3: 21. Google Scholar
- 14 : Differential diagnosis of complex cystic renal mass using multiphase computerized tomography. J Urol2009; 181: 2446. Link, Google Scholar
- 15 : Malignant renal cysts: diagnostic performance and strong predictors at MDCT. Acta Radiol2010; 51: 590. Google Scholar
- 16 : Is it safe and effective to treat complex renal cysts by the laparoscopic approach?. J Endourol2011; 25: 471. Google Scholar
- 17 : Differential diagnosis of complex renal cysts based on lesion size along with the Bosniak renal cyst classification. Yonsei Med J2012; 53: 729. Google Scholar
- 18 : Development of a clinical prediction model for assessment of malignancy risk in Bosniak III renal lesions. Urology2013; 82: 630. Google Scholar
- 19 : Therapeutic strategy of Bosniak category II renal cyst: a report of 52 cases. Zhonghua Yi Xue Za Zhi2013; 93: 1897. Google Scholar
- 20 : Bosniak category III cysts are more likely to be malignant than we expected in the era of multidetector computed tomography technology. J Res Med Sci2014; 19: 634. Google Scholar
- 21 : Pathological characteristics and radiographic correlates of complex renal cysts. Urol Oncol2014; 32: 1010. Google Scholar
- 22 : Follow-up CT of moderately complex cystic lesions of the kidney (Bosniak category IIF). AJR Am J Roentgenol2003; 181: 627. Google Scholar
- 23 : Complex cystic renal masses: characterization with contrast-enhanced US. Radiology2007; 243: 158. Google Scholar
- 24 : Multislice computed tomography versus contrast-enhanced ultrasound in evaluation of complex cystic renal masses using the Bosniak classification system. Clin Hemorheol Microcirc2008; 39: 171. Google Scholar
- 25 : Radiologic-pathologic correlations of intratumoral tissue components in the most common solid and cystic renal tumors. Pictorial review. Eur Radiol2005; 15: 1734. Google Scholar
- 26 : Radiographic surveillance of minimally and moderately complex renal cysts. BJU Int2009; 103: 1116. Google Scholar
- 27 : Bosniak category IIF designation and surgery for complex renal cysts. J Urol2009; 182: 1091. Link, Google Scholar
- 28 : Interpersonal variability and present diagnostic dilemmas in Bosniak classification system. Scand J Urol Nephrol2011; 45: 239. Google Scholar
- 29 : Clinical outcomes of Bosniak category IIF complex renal cysts in Korean patients. Korean J Urol2012; 53: 386. Google Scholar
- 30 : Bosniak category IIF and III cystic renal lesions: outcomes and associations. Radiology2012; 262: 152. Google Scholar
- 31 : Bosniak IIF renal cysts: is there a malignancy potential?. J Clin Urol2013; 6: 106. Google Scholar
- 32 : Evaluation of Bosniak category IIF complex renal cysts. Insights Imaging2013; 4: 471. Google Scholar
- 33 : Progression, interobserver agreement, and malignancy rate in complex renal cysts (≥Bosniak category IIF). Urol Oncol2014; 32: 24. Google Scholar
- 34 : Follow-up for Bosniak category 2F cystic renal lesions. Radiology2014; 272: 757. Google Scholar
- 35 : Outcomes and complications related to the management of Bosniak cystic renal lesions. AJR Am J Roentgenol2015; 204: W550. Google Scholar
- 36 : Management, pathology and outcomes of Bosniak category IIF and III cystic renal lesions. World J Urol2015; 33: 295. Google Scholar
- 37 : MRI evaluation of complex renal cysts using the Bosniak classification: a comparison to CT. Abdom Radiol (NY)2016; 41: 2011. Google Scholar
- 38 : The role of Bosniak classification in malignant tumor diagnosis: a single institution experience. Investig Clin Urol2016; 57: 100. Google Scholar
- 39 : Atypical renal cysts. Tunis Med2015; 93: 386. Google Scholar
- 40 : Interobserver variability in determining enhancement of renal masses on helical CT. AJR Am J Roentgenol1999; 172: 1207. Google Scholar
- 41 : Enhancing component on CT to predict malignancy in cystic renal masses and interobserver agreement of different CT features. AJR Am J Roentgenol2006; 186: 665. Google Scholar
- 42 : Characterization of atypical cystic renal masses with MDCT: comparison of 5-mm axial images and thin multiplanar reconstructed images. AJR Am J Roentgenol2010; 195: 693. Google Scholar
- 43 : Bosniak classification system: inter-observer and intra-observer agreement among experienced uroradiologists. Acta Radiol2015; 56: 374. Google Scholar
- 44 : Multilocular cystic renal cell carcinoma: comparison of imaging and pathologic findings. AJR Am J Roentgenol2012; 198: W20. Google Scholar
- 45 : Cystic renal cell carcinomas: do they grow, metastasize, or recur?. AJR Am J Roentgenol2013; 201: W292. Google Scholar
- 46 : An outcome prediction model for patients with clear cell renal cell carcinoma treated with radical nephrectomy based on tumor stage, size, grade and necrosis: the SSIGN score. J Urol2002; 168: 2395. Link, Google Scholar
- 47 : CT-guided biopsy of indeterminate renal cystic masses (Bosniak 3 and 2F): accuracy and impact on clinical management. Eur Radiol2002; 12: 2518. Google Scholar
- 48 : Prospective analysis of intraoperative frozen needle biopsy of solid renal masses in adults. J Urol1999; 162: 1282. Link, Google Scholar
- 49 : Application of TNM, 2002 version, in localized renal cell carcinoma: is it able to predict different cancer-specific survival probability?. Urology2004; 63: 1050. Google Scholar
- 50 : Cystic renal cell carcinoma carries an excellent prognosis regardless of tumor size. Urol Oncol2015; 33: 505. Google Scholar
