Malignant Progression Outcomes of Bosniak Graded Renal Cysts in the Modern Era of Better Imaging and Uro-Radiology Subspecialisation

Objective The Bosniak grading system is used to help clinicians manage renal cysts by predicting malignant potential; however, its limitations include variable reported malignancy rates, particularly in Class IIF. Initially, these cysts were predicted to have a malignant potential of 18.5% therefore, they are followed up for at least five years. The aim of this study was to provide the outcome of Bosniak graded cysts in the modern era of CT imaging and uro-radiology subspecialisation to assess the malignant potential of each class. Methods A total of 379 Bosniak graded cysts were analyzed over a five-year period, with a median follow-up of 11.2 months. Malignant potential was calculated based on radiological progression or histopathology. Results Subsequent malignant transformation rates were 0% in category 1, 1.70% in category 2, 3.96% in category 2F, 27.78% in category 3, and 61.54% in category 4. Conclusion This study adds to the growing body of evidence that Bosniak cysts, especially Class IIFs, are less malignant than previously thought. Stringent evaluation of these cysts in dedicated renal multidisciplinary teams (MDTs) is to be encouraged along with further research. This will contribute to a refinement of the follow-up guidelines to ensure they are both appropriate and safe.