Multilocular cystic renal tumor in children: radiologic-pathologic correlation.

Multilocular cystic renal tumor is a term that encompasses two histologically distinct but grossly indistinguishable lesions: cystic nephroma and cystic partially differentiated nephroblastoma (CPDN). Cystic nephroma is a segmental, purely cystic mass characterized by multiple septations composed entirely of differentiated tissues, without blastemal elements. CPDN is also a multiloculated lesion without nodular solid components, but its septa contain embryonal cells. Multilocular cystic tumors primarily affect boys during early childhood, with a substantial number of the lesions containing blastema (CPDN), and adult women, with lesions that more commonly lack septal blastema (cystic) nephroma). As a rule, nephrectomy is curative and the clinical course benign, but CPDN may recur locally. Although cystic nephroma and CPDN cannot be distinguished radiologically, failure to do so has no practical impact on management, since all of these tumors are surgically removed. However, the differential diagnosis includes other pediatric cystic renal masses that may require different treatment stratagems: Wilms tumor with cyst formation due to hemorrhage and necrosis, cystic clear cell sarcoma, cystic mesoblastic nephroma, cystic renal cell carcinoma, multicystic dysplastic kidney, and segmental multicystic dysplasia in a duplicated renal collecting system.