[A case of renal malacoplakia that was difficult to distinguish from cystic renal cell carcinoma].

A 66 years old man visited our hospital with a chief complaint of right flank pain and abdominal palpable mass. Abdominal enhanced computed tomography scan showed a large cystic mass with infiltrating surrounding tissue in the right kidney. We diagnosed it infected cystic renal cell carcinoma because of high grade fever and acute inflammatory response. It was surgically unresectable tumor. Therefore, percutaneous puncture and drainage was performed under ultrasound guidance. In the culture of drainage fluid, Escherichia coli (E. coli) was isolated. Then, we confirmed reduction in the size of the tumor, right radical nephrectomy was performed. Because of tumor invasion to ascending colon, we performed the excision of right kidney together with ascending colon. Histological study confirmed target-shaped Michaelis-Gutmann body, and the definitive diagnosis was malacoplakia of the kidney. We reported a case of renal malacoplakia that was difficult to distinguish from cystic renal cell carcinoma. Our case is 12th case of renal malacoplakia in the Japanese literature.