A case of nephroblastoma (Wilms' tumor) which grossly and microscopically simulated sarcoma botryoides embryonal rhabdomyosarcoma is presented. Macroscopic examination of the nephrectomy material revealed a grape-like tumor occupying the left renal pelvis and colyceal system and which had the macroscopic appearance of botryoid sarcoma. Although preliminary microscopic examination simulated botryoid sarcoma, further examination of the multiple sections taken from different sites of the tumoral mass revealed metanephritic blastemic epithelial and mesenchymal components confirming the diagnosis of Wilms' tumor. No tumoral mass was demonstrable in the renal parenchyma. The involved kidney appeared to be hypoplastic, four columns of Bertin being recognized.

Keywords: Botryoid nephroblastoma, Wilms' tumor, hypoplastic kidney