[Botryoid Wilms tumor extending into the duodenum].

We report on a rare case of botryoid Wilms tumor extending into the duodenum. This uncommon macroscopic form of nephroblastoma consists entirely of a polypoid renal intrapelvic mass. The main differential diagnosis of this unusual tumor is botryoid rhabdomyosarcoma. A 14-month-old boy presented with a painful abdominal mass. Radiology revealed a large heterogeneous mass in the renal calyx, protruding into the ureter. A right radical nephroureterectomy was carried out. The tumor was found to extend into the 2nd portion of the duodenum. The pathologic diagnosis was mixed type nephroblastoma, SIOP 2001 stage III. The patient was given a course of postoperative chemotherapy. No local recurrence or metastatic spread has been detected after 2 years. Only few such cases have been previously reported, some of them extending into the bladder. To our knowledge, botryoid nephroblastoma has not previously been described as extending into the digestive system.