Cystic dysplasia of the testis. Light and electron microscopic study of three cases.

The testes of two premature newborns and a 9-year-old boy with cystic dysplasia were studied by light and electron microscopy. The histologic pattern of the three cases was similar, differing principally in the extension of the characteristic lesion. This consisted of multiple, anastomosing, irregular cystic spaces of varying sizes and shapes, separated by incomplete connective-tissue septa. The cysts were predominantly located in the mediastinum testis, and spread irregularly, displacing the testicular parenchyma, which was consequently compressed under the tunica albuginea. Electron microscopic examination revealed two types of epithelial cells (flattened and tall cells) lining the cystic spaces. These cells were similar to those lining the normal adult rete testis. Since the rete testis originates from the gonadal blastema, and the efferent ductules from the mesonephric ducts, an embryologic defect in the connection between both structures might be responsible for this lesion.