Objectives  To analyze the clinicopathologic features and the prognostic factors of nephroblastomas (Wllms' tumor).

  Methods  A database was established for nephroblastoma cases admitted from January 200l to December 2007 in the Department of Surgical Oncology, Beijing Children's Hospital.

  Results  A sample of A total of 61 boys (60%) were enrolled into the study. The median age was 3.16 years. The most common symptom was abdominal mass. Among the 92 patients with surgical treatment, 88 cases underwent typical nephrectomy. The clinical staging of the patients were as follows: 37 cases (41%) were in stage I, 22 cases (25%) were in stage III. Histopathology indicated 76 cases with favorable histology (FH) and 1 case had an unfavorable histology (UFH). The overall survival rate was 78.9%. The median follow-up time was 76.7 months. Staging was the most important factor associated with prognosis. One case of horseshoe kidney and seven cases of other congenital malformation were reported.

  Conclusion  Up to 85% of the patients reported an onset before 5 years old. The most common symptom was abdominal mass. The right side of the kidney is more commonly involved than the left. Stage 1 and III were more common among the study population. FH is the major type in histopathology. The most common metastatic sites were the lungs and liver. In this group, the overall survival rate was 78.9%. Staging was the main prognostic factor. The special type of Wilms' tumor in a horseshoe-kidney. Some malformation were also associated with nephroblastoma.