Cystic renal cell carcinomas in adults. Is preoperative recognition of multilocular cystic renal cell carcinoma possible?

Purposes: We correlated clinicopathological and imaging features of multilocular cystic renal cell carcinoma (MCRCC) to propose preoperative criteria for therapeutic modalities. Materials and Methods: A total of 24 RCCs with a chiefly cystic component were identified from 1993 to 2002. In each case histological slides and available imaging studies were retrieved. Two tumor groups were defined, namely MCRCC and clear RCC with cystic change (CRCC) by intrinsic growth or necrotic degeneration. Radiological correlation using computerized tomography and magnetic resonance imaging was performed considering criteria such as an expansile nodule, cyst wall thickness and septa. Results: On imaging MCRCC presented as a multilocular cystic mass lacking an expansile nodule, and with regular thin cyst wall and septa. On pathological study MCRCC presented as complex, multilocular cystic carcinoma with septa covered by low nuclear grade clear renal tumor cells without a grossly expansile nodule. They were staged pT1 with a free clinical course. In contrast, CRCC was identified on imaging with an expansile nodule (5 mm or greater), thick, irregular cyst wall and septa. On pathological study CRCC was characterized by a grossly expansile nodule in the septa and/or cyst wall. Nuclear grade and TNM stage were higher in CRCC. Conclusions: Preoperative recognition of MCRCC is possible using strict computerized tomography and/or magnetic resonance imaging criteria. The current study confirms the low malignant potential of MCRCC. Nephron sparing surgery should be proposed when MCRCC is suspected.