An unusual renal malignancy of childhood: unilateral teratoid Wilms's tumor.

Teratoid Wilms's tumor is a rare histologic variant of the classical Wilms's tumor, containing predominantly heterolougus tissues (adipose, glial, muscle, cartilage, or bone). We report an unusual variant of such tumor, which simulated renal teratoma because of abundant fat within the tumor. The child underwent radical excision; postoperatively, he was treated with chemotherapy, and now the child is well at 36 months after surgery. The behavior of this kind of tumor usually is not aggressive, and the outcome is good. Surgery should be the treatment of choice, because the efficacy of chemotherapy and radiotherapy is probably reduced by the high amount of differentiated and mature tissue that characterizes this neoplasm. Radiologic imaging and pathological features of this rare entity are described.