Adult teratoid Wilms' tumor with prominent neuroepithelial differentiation.

Teratoid Wilms' tumor is a rare variant of Wilms' tumor (WT) that has been reported exclusively in pediatric patients. The present paper describes a teratoid WT in a 50-year-old Korean man with a giant right renal mass. Radical nephrectomy was performed under the impression that the mass was a renal cell carcinoma. Grossly, the removed kidney contained a giant well-encapsulated mass measuring 24 x 18 x 10 cm with cystic changes, necrosis, and hemorrhage. On microscopy triphasic patterns of WT and prominent heterologous components were seen, including rhabdomyoblasts, neuroepithelial tissue, fat, cartilage, and various types of mature epithelium. This is the first reported case of a teratoid WT occurring in an adult kidney.