Rhabdomyosarcoma of the kidney in children.

Among 227 consecutive renal tumors examined from the Hospital de Niños de Buenos Aires, seven examples of a distinctive clinicopathological entity occurred. These renal neoplasms were all unilateral, grossly infiltrative without a definitive capsule. Microscopically, the lesion was characterized by a sarcomatous pattern with a rhabdomyoblastic differentiation. Four of them had regional lymph node involvement at surgery. Four developed bone metastases and none had lung metastases. In three instances, the bone metastases were histologically similar to the original neoplasm. The age of the patients ranged from 11 months to 5 1/2 years. A male predominance was observed. Two patients died; one is alive 5 years after surgery; three are alive with metastases; one has been followed for less than a year. In this study, it is proposed that another group of tumors be removed from the Wilms' tumor classification. The neoplasm has been described previously in the literature under several names. It is not clearly related clinicopathologically to nephroblastoma. The term rhabdomyosarcoma is proposed in view of its entirely different biological behavior.