Benign cystic nephroblastoma.

A benign cystic nephroblastoma in a 6-month-old boy is presented. Erroneous interpretation as malignant nephroblastoma led to unnecessarily aggressive therapy. There is no evidence of recurrence or metastatic disease 12 years after the initial resection. As shown in our case and in the others previously reported in the literature, benign cystic nephroblastoma represents a distinct clinicopathological entity which does not show malignant behavior.