[Complex renal cyst. A new case]

Approximately 15% of cases of renal cell carcinoma present cystic configuration on radiologic and pathologic examination. These lesions are often difficult to differentiate from the multiloculated renal cyst or other benign cystic lesions such as hemorrhagic cyst and so on. We report a case of multilocular cyst of the right kidney complicated with clear cell type renal cell carcinoma in which MRI suggested benign cyst. The diagnosis of complicated benign cyst must be proposed very cautiously and the persistence of doubtful images justifies surgical exploration.