RESUMEN
Cystic dysplasia of the rete testis (CDRT) is a very rare cause of a paediatric scrotal mass often associated with renal and other genitourinary tract anomalies. These complex malformations are probably due to a developmental defect of the mesometanephric system during embryogenesis. A case of asymptomatic scrotal swelling in a 4-year-old boy is presented. Ultrasonography, showed a cystic lesion of the left testis associated with absence of the left kidney. Orchiectomy was performed because of extensive gonad involvement. Pathologic examination revealed multiple, anastomosing, irregular cystic spaces of varying sizes and shapes predominantly located in the region of the rete testis. The cysts had spread irregularly, displacing the testicular parenchyma, which was subsequently compressed under the tunica albuginea. Preoperative diagnosis of CDRT is easy if age, precise localisation, characteristic ultrasonographic features and other genitourinary malformations are considered. Other paediatric cystic lesions should be included in the differential diagnosis. It is possible to cure CDRT by orchiectomy or by conservative treatment. Nowadays the later option is preferred, but diagnosis of CDRT must be precisely established and followed by careful monitoring.