Non-Wilms' renal tumors in children.

Renal tumors other than Wilms' tumors are infrequent in childhood. Wilms' tumors account for 6% to 7% of childhood cancer, whereas the remaining renal tumors account for less than 1%. The most common non-Wilms' tumors are clear cell sarcoma of the kidney, rhabdoid tumor of the kidney, renal cell carcinoma, mesoblastic nephroma, and multilocular cystic nephroma. Collectively, these tumors account for less than 10% of the primary renal neoplasms in childhood.