Wilms' tumor: a search for the critical lesion

A Wilms' tumor from a 12-month-old boy showed epithelial and mainly rhabdomyoblastic differentiation. In addition, the kidney contained foci of nephroblastomatosis, a lesion predisposing to the development of nephric tumors. Flow cytometry indicated that the tumor DNA content was in the diploid range with an increased S-phase. Chromosome studies of the cultured tumor cells showed a dominant pattern of 49,XY, +8,9qh+, +12, +12,18q+, without obvious deletion of 11p. A few cells showed additional losses, deletions, or structural rearrangements superimposed on the basic pattern, but no normal metaphases were observed. The DNA from the tumor was probed for several loci on 11p because variations of 11p (deletion or translocation) have been reported in roughly one third of Wilms' tumors, and the critical gene in Wilms' has been localized to 11p13. In this case, 11p genes maintained heterozygosity or showed no detectable alteration in gene dosage when compared with peripheral-blood DNA. Therefore, despite histologic indication of an underlying constitutional defect, no genomic lesion of 11p was identified.