[Immunohistochemical identification of testicular germ cells--preliminary report]

The use of testicular spermatozoa for intracytoplasmic sperm injection introduced a new treatment modality for management of male infertility. Since testicular biopsies of non-obstructive azoospermic men are not homogenous in their histological patterns, identification with certainty of focal spermatogenesis might be difficult, particularly in those with small foci of spermatogenesis. We used an immunohistochemical marker of the male germ line, an antibody generated against RBM (RNA-binding-motif), to recognize with high precision the presence of germ cells in the biopsy. Biopsies of 30 men with azoospermia, most with non-obstructive azoospermia and a few with obstruction of the vas deferens, were evaluated. Immunohistochemical staining for RBM protein contributed to the detection and accuracy of the identification of germ cells. Furthermore, this immunohistochemical technique aided the histopathologist to focus on even small foci of spermatogenesis. Absence of the protein expression confirmed the diagnosis of Sertoli-cell-only syndrome. The results indicate that expression of RBM can be a diagnostic marker for identifying the germ cells of small concentrations of spermatogenesis. This method can enhance the accuracy of histopathological evaluation of testicular biopsies that had formerly relied mainly on hematoxylin-and-eosin staining.