Cystic dysplasia of the testis.

Cystic dysplasia of the testis (CDT) is a rare congenital defect that results in the formation of numerous irregular cystic spaces within the mediastinum testis. We describe a 4-year-old boy with right testicular swelling who underwent orchiectomy for CDT after a preoperative ultrasound examination revealed a multicystic, anechoic lesion. Grossly, the lesion was 2 cm in size and was composed of multiple, irregularly shaped cystic spaces lined by flattened cuboidal epithelium. Immunohistochemical studies revealed that the epithelial cells expressed keratin, vimentin, and epithelial membrane antigen. Both the histologic appearance of the cyst lining and the immunohistochemical profile resembled the epithelium of rete testis. In our review of the literature 10 cases (including this lesion) of CDT have been described. A defect in the connection between the efferent ductules, derived from the mesonephric epithelium, and the rete testis and seminiferous tubules, derived from the gonadal blastema, is currently thought to be the most likely explanation of the pathogenesis of CDT.