Diffuse persistent glomerular immaturity and focal proximal tubular ectasia were seen in bilateral open renal biopsy specimens for an infant with fluid and salt depletion and slowly progressive renal failure. Subsequently, diffuse tubulopapillary renal adenoma subtotally replaced each kidney, thereby, necessitating renal transplantation. Origin of diffuse metanephric adenoma from persistent primitive epithelium of the proximal nephron is postulated and partly substantiated. We propose that this case of persistent proximal nephronic epithelial immaturity and diffuse metanephric adenoma is a variant of nephroblastomatosis and that in this case, a first trimester suicide attempt with aspirin may have initiated the maturation defect that preceded neoplastic transformation.