Cystic renal masses are commonly encountered in daily clinical practice. Improvements in the resolution of imaging modalities have led to an improved ability to detect cystic renal masses. It is important for radiologists to recognize and appropriately characterize cystic renal masses. Since 1986, the Bosniak classification system has been widely accepted for the evaluation of cystic renal masses, portions of which have been revised in 2019. Although the Bosniak classification system cannot fully differentiate aggressive lesions from indolent lesions, the system may help improve the specificity of detection for higher-risk classes for malignancy, increase the proportion of masses that are surveilled or ignored rather than resected, and select optimal management strategies.
