Immunohistochemistry: Additional armamentarium in the management of polyorchidism.

A 11-year-old boy had long-standing, asymptomatic para-testicular mass inside the left hemiscrotum. Physical examination identifi ed a double, superimposed, non-adherent scrotal mass. Color Doppler ultrasonography indicated normoechogenic homolateral testes and epididymides, with individual blood vessel networks. The right testis measured 40 × 19 mm; on the left, the lower testis was 21.8 × 15.2 mm; and the upper one, 17.5 × 12.7 mm ( Fig. 1 ). At surgery, left scrotal exploration indicated two separate testes within a single tunica vaginalis. Both testes had their own epididymis, vas deferens and vessels. The two vasa joined together within the operative fi eld to form a common vas ( Fig. 2 ). After biopsies of the left testes a double orchidopexy was performed. HE histology and immunocytochemistry using c-kit and CD99 rabbit antibodies were carried out. On light microscopy the upper left testis was found to have post-pubertal seminiferous tubules, with mature Sertoli and germ cells, including round and/or long spermatids ( Fig. 3a ). In contrast, the lower left testis had empty or variously depleted seminiferous tubules, because spermatogonia and Sertoli cells were detached from the basal lamina, and thickened peritubular layer often occurred ( Fig. 3b ). As regards CD99 expression, a strong cytoplasmic immunostaining of Sertoli cells was common in both left testes. On the basis of CD99 immunostaining, MSI in 50 transverse sections of seminiferous tubules was counted to be 7.7 ± 2.0 in the upper testis and 3.5 ± 1.2 in the lower one. On Student’s t -test the MSI difference between the study testes was found to be signifi cant ( P < 0.001). Moderate c-kit immunostaining of endotubular cells in the upper left testis ( Fig. 3c ) contrasted with a weak, focal c-kit positivity in the lower one ( Fig. 3d ). Patient Report