Teratoid Wilms' tumor: a case report with literature review.

Teratoid Wilms' tumor is an unusual histologic variant of nephroblastoma in which the heterologous tissue predominates. The treatment for this tumor has not been established because of its rarity and varying tumor components. The authors report a case of localized teratoid Wilms' tumor in a 4-month-old male infant successfully treated with nephrectomy only. The tumor originated from the right kidney with multiple cysts and calcifications; renal teratoma was suspected preoperatively, and the operation was performed. The tumor was excised completely, and the specimen weighed 340 g. Histopathologic examination showed that various teratoid elements occupied most of the tumor with sparse islands of triphasic nephroblastoma, which was consistent with teratoid Wilms' tumor. Anaplastic elements, tumor capsule invasion, renal sinus soft tissue invasion, or tumors in intrarenal vessels were not observed. The patient was disease free for 3 years after surgery without receiving chemotherapy. We selected this therapeutic approach because of the chemoresistance of this tumor and the excellent prognosis in small (<550 g) stage I/favorable-histology classical Wilms' tumor diagnosed at less than 24 months of age. Therefore, nephrectomy alone may be an acceptable treatment of this stage of tumor in patients with teratoid Wilms' tumor.