Purpose: Cystic partially differentiated nephroblastoma is a rare variant of Wilms tumor, and might be confused with cystic nephroma. Definitive diagnosis can only be made by histological examination. Therefore, initiation of therapy, either primary nephrectomy or preoperative chemotherapy, might create a dilemma when radiological diagnosis is doubtful.
Materials and methods: To define treatment strategies for these entities, we reviewed the records of 1,245 patients enrolled in SIOP (International Society of Pediatric Oncology) trials 93-01 and 2001 GPOH (German Society of Pediatric Oncology and Hematology) between July 1993 and August 2004. Data were collected retrospectively. Therapy, outcome and preoperative management were evaluated. To confirm diagnosis of cystic nephroma/partially differentiated nephroblastoma, all patients underwent review by the Reference Pathology Center of SIOP/GPOH.
Results: A total of 14 patients with diagnoses of cystic nephroma (7) and cystic partially differentiated nephroblastoma (7) were identified. Median patient age at diagnosis was 1 year (0.46 to 3). Two patients received preoperative chemotherapy. Primary nephrectomy was performed in 12 patients. Two patients underwent partial nephrectomy. In 1 child postoperative chemotherapy was administered. None of the patients had progression of disease or recurrence. Overall survival was 100%. Median followup was 2.41 years (0.3 to 9).
Conclusions: In cystic renal tumors radiological findings should always be reviewed by the reference radiologist of the treatment protocol study group. Irrespective of the chosen therapy, outcome of cystic nephroma and cystic partially differentiated nephroblastoma is favorable. Even in large international trials the number of patients with cystic nephroma or cystic partially differentiated nephroblastoma is too small for statistical analysis.