Correlation between a specific Wilms tumour suppressor gene (WT1) mutation and the histological findings in Wilms tumour (WT).

W ilms tumour (WT) is the most common malignant neoplasm of the kidney in childhood and accounts for approximately 8% of all childhood solid tumours. 2 Fetal rhabdomyomatous nephroblastoma (FRN) is a histological variant of WT characterised by a predominance of rhabdomyogenic components. Clinically, WT of the FRN type presents as a huge mass in younger patients and about 30% of them have bilateral disease. The tumour rarely metastasises or shows aggressive behaviour and it has a good prognosis. The Wilms tumour suppressor gene (WT1) on chromosome 11p13 was identified in 1990 and encodes a transcriptional factor containing a domain of four zinc finger motifs. 5 Schumacher et al reported that a germline mutation in WT1 predisposes to the development of tumours with stromal predominant histology. We analysed germline and tumour WT1 in seven cases of WT that were diagnosed as FRN histologically, or contained rhabdomyogenic components, and found the same mutation in five of them.