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

## TL;DR

This study evaluates the cancer risk of kidney cysts using the Bosniak system and finds that some cysts are less likely to become cancerous than previously believed.

## Contribution

The study provides updated malignancy rates for Bosniak cysts in the modern era of advanced imaging and specialized radiology.

## Key findings

- Category IIF cysts had a 3.96% malignant transformation rate, lower than the previously estimated 18.5%.
- Malignant transformation rates increased with higher Bosniak categories, reaching 61.54% in category 4.
- The study supports the need for refined follow-up guidelines for Bosniak cysts based on modern imaging and multidisciplinary evaluation.

## Abstract

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.