Background. According to national and foreign publications, renal cyst is one of the most common urological diseases with a prevalence up to 20–50%.
Aim. To determine the results of surgical treatment of patients with renal cysts, depending on the risk of malignancy.
Materials and methods. The analysis of 124 patients with symptomatic renal cysts who were treated in the Department of Urology of Regional Clinical Hospital was carried out. All patients underwent a comprehensive clinical and instrumental evaluation, including contrast-enhanced CT scan of the kidneys. To assess the risk of harboring malignant tumor, the classification of renal cysts of Bosniak (2019) was used.
Results. The average age of patients was 56.6±12 years. According to CT, Bosniak I, II, IIF and III cysts were diagnosed in 96 (77.4%), 11 (8.9%), 11 (8.9%) and 6 (4.8%) patients, respectively. The morphologic study revealed renal cell cancer in 8 patients (6.4%), four of whom had Bosniak III cysts and other four had Bosniak IIF cysts.
Discussion. The prediction of the harboring of malignancy is a fundamental criterion for selection of patients with renal cysts for surgical treatment.
Conclusion. Surgical treatment of symptomatic renal cysts is a justified treatment method, and in patients with Bosniak class II or higher cysts, it is necessary to exclude the malignant lesion. Based on our data, category IIF and III cysts have a high risk of harboring malignant cells, which is 36.4% and 66.7%, respectively. In our opinion, laparoscopic partial nephrectomy is the most rational treatment method in these categories.

Keywords: malignant transformation of renal cysts, Bosniak classification, renal cysts, renal cell carcinoma