[Multi-locational cystic mass of the kidney: a diagnostic challenge].

Multilocular cystic masses of the kidney present a diagnostic challenge because they may be malignant. Renal cell carcinoma with multilocular cysts has been reported. We present 4 cases in which the preoperative differential diagnosis was between a benign and a malignant multilocular cystic kidney mass. Our results, combined with those of 33 previously reported cases, reveal that only 32% of cases were diagnosed correctly preoperatively. In 21% of these patients the preoperative clinical evaluation did not correctly diagnose malignancy: 24% of them yielded false negative and 21% false positive results. Angiography was more accurate than CT, US or aspiration of cysts. Frozen section was inaccurate in 55% of cases. There is no reliable diagnostic test to distinguish between a malignant and a benign multilocular cystic mass. Invasive angiography is more accurate than other modalities. A therapeutic decision has to be made between nephron-sparing and radical surgery in each case. When nephron-sparing surgery is considered, the possible need to perform radical nephrectomy in second-look surgery must be taken into account.