Paratesticular metastasis from Wilms tumor associated with a hydrocele.

Metastatic sites other than the lungs, lymph nodes, and liver are unusual for Wilms tumor (WT). Intra-scrotal metastasis is very rare. We report a 3-year-old boy with stage IIA WT, who experienced paratesticular metastasis 2 months after surgery for an abdominal recurrence. He had right scrotal hydrocele at initial diagnosis. The patient underwent right radical orchiectomy, and pathological examination revealed paratesticular WT metastasis. Intra-abdominal and peritoneal disseminated metastases followed. We considered that tumor cells spread through the patent processus vaginalis and grew at paratesticular space in hydrocele. One month after the end of 12 months of salvage chemotherapy and abdominal radiotherapy, the patient has no evidence of disease.