[A case of small simple renal cyst associated with renal cell carcinoma]

A 61-year-old male was admitted to our clinic for the purpose of further examination of the small renal mass discovered incidentally by ultrasonography. Subtraction angiography disclosed a small renal cell carcinoma of the upper-lateral margin of the left kidney dramatically. Enucleating surgery of the tumor was performed successfully (about 2 cm in diameter). Histological examination revealed a small simple renal cyst associated with renal cell carcinoma. The patient is well without evident metastasis 1 year postoperatively. Since this is a very rare case in the literature, we report this case and discuss the preoperative diagnosis of small renal cell carcinoma. We believe that ultrasonography is a simple and very useful method for mass screening of small urological malignancies.