A Case of Primary Paratesticular Wilms Tumor in an Undescended Testis.

Extrarenal Wilms tumor is rare. We describe the first reported case of primary paratesticular extrarenal Wilms tumor with regional metastasis in 8-month old male with left undescended testis. Patient underwent left radical orchiectomy with regional lymph node excision. The inguinal node and paratesticular mass demonstrated the classic Wilms triphasic pattern, stained positively for WT-1 and demonstrated no loss of heterozygosity of chromosomes 1p and 16q. Work-up was negative for primary renal Wilms tumor or distant metastasis. Patient underwent adjuvant chemoradiation therapy for stage III disease. Patient is currently 2 years of age with no evidence of recurrence or metastatic disease.