[Co-existence of renal cyst and tumor: report of two cases and a review of the literature].

We report on two patients with renal cyst and tumor in the same kidney. Despite the diagnosis of benign renal cyst obtained by radiological investigation, one case proved to be malignant at surgical exploration. The other patient was diagnosed to have renal cyst and tumor in the same kidney preoperatively. Co-existence of renal cyst and tumor is considerably rare. Thirty four cases collected from the Japanese literature, including our two cases, are reviewed and discussed.