Cystic renal masses are very commonly diagnosed with the widespread use of imaging. The current treatment paradigm contributes to overtreatment, with biopsy accuracy being limited. The currently used definitions of renal cysts are quite limited.
The Bosniak classification is a CT-established classification initially conceived in 1986, with Bosniak 1+2 being benign and Bosniak 4 regarded as malignant.1 It was later updated in 2012 with the addition of Bosniak 2F, which is likely benign, and Bosniak 3 considered as indeterminate2 (Table 1).
Table 1 - Current utilized Bosniak classification:3
Dr. Wells moved on to discuss the Bosniak version 2019 update. The aim of this new version that has not been approved yet was to reduce inter-reader variability, especially across Bosniak 2, 2F, and 3 cystic masses. Additionally, the goal was to improve the variability of reported malignancy rates, especially across Bosniak 2F and 3 cystic masses,4 and establish clearly defined diagnostic criteria for CT and MRI.3
The main updates to the 2019 Bosniak update are shown in Figure 1 and Figure 2.
Figure 1 - Bosniak 2019 update:
Figure 2 – Bosniak version 2019 update:
In the 2019 version, update 1-3 septations are considered as Bosniak 2, and if there are 4 or more septations, it is a Bosniak 2F. Calcifications are now considered as Bosniak 2. In this new updated version, mass size is not included as it is understood that the changes in morphology are much more important.
Ultrasound is not officially included in the 2019 updated version, as it has been shown to result in an approximately 25% rate of up-classifying when compared to CT scan.
Dr. Wells concluded his talk by stating that the version 2019 Update of the Bosniak classification should enhance the clarity and specificity of cystic renal mass characterization.
Presented by: Shane Wells, MD, Associate Professor, University of Wisconsin, Madison, WI
Written by: Hanan Goldberg, MD, MSc, Assistant Professor, Urology Department, SUNY Upstate Medical University, Syracuse, NY, USA @GoldbergHanan at the 2020 Society of Urologic Oncology Annual Meeting – December 2-5, 2020 – Washington, DC
References:
- Bosniak MA. The current radiological approach to renal cysts. Radiology 1986; 158(1): 1-10.
- Bosniak MA. The Bosniak renal cyst classification: 25 years later. Radiology 2012; 262(3): 781-5.
- Silverman SG, Pedrosa I, Ellis JH, et al. Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment. Radiology 2019; 292(2): 475-88.
- Schoots IG, Zaccai K, Hunink MG, Verhagen P. Bosniak Classification for Complex Renal Cysts Reevaluated: A Systematic Review. The Journal of urology 2017; 198(1): 12-21.