Wilms' tumour associated with deep cystic nephroma-like changes: three cases of a putative Wilms' tumour precursor.

We describe three cases of Wilms' tumour accompanied by central pericalyceal multicystic lesions closely resembling those seen in cystic nephroma. In continuity with these lesions or elsewhere in the kidney were areas of dysplastic renal tissue of the type sometimes referred to as intralobar nephroblastomatosis. A close homology of tissue differentiation was observed between the dysplastic lesions and the interstitial components of the cystic lesions. These findings support the hypothesis that, in some cases at least, cystic nephroma has more in common with the group of dysplastic lesions referred to as the nephroblastomatosis complex than with the true renal tumours of childhood.