Teratoid Wilms' tumor: report of a unilateral case.

A unilateral teratoid Wilms' tumor was removed 2.5 weeks after the institution of chemotherapy. Teratoid Wilms' tumor is an extremely rare renal tumor, and only four cases, all bilateral, have been reported. Because of the finding of deep cortical intralobar nephroblastomatosis, strongly associated with bilateral Wilms' tumors, the patient has been closely followed since surgery without evidence of tumor in the remaining kidney at 2 years.