Partial nephrectomy for a Bosniak IV cystic renal mass mimicking a simple renal cyst adjacent to a solid renal tumor

Introduction: Renal tumors are often associated with renal cysts. Meanwhile, in some cases there are challenging issues of how to diagnose renal cystic tumors and to decide surgical procedures.

Case presentation: A 75-year-old man was referred to our department for a 21-mm tumor by his left kidney. Contrast-enhanced computed tomography showed an intense contrast uptake the tumor, which was adjacent to a 64-mm unilocular renal cyst with no contrasting effects. It was clinically diagnosed as renal cell carcinoma, stage T1aN0M0, and treated with robot-assisted partial nephrectomy, for both the solid tumor and the adjacent cyst. Pathological findings revealed a tumor cell clump within the cyst wall, concurrent with the renal cell carcinoma. The patient has remained free of disease at 1 year after surgery.

Conclusion: A partial nephrectomy that includes the entire cyst wall should be considered for renal tumor associated with unilocular renal cyst.