The contribution of RNA-binding motif (RBM) antibody to the histopathologic evaluation of testicular biopsies from infertile men

Testicular biopsies of infertile men are often characterized by mixed histo logic patterns, with different types of spermatogenic impairments being fou nd in adjacent seminiferous tubules. RNA-binding motif (RBM) is a nuclear p rotein expressed exclusively in the male germ cell line. We reasoned that R BM might be a useful marker to identify germ cells in testicular sections, particularly in biopsies with mixed histologic phenotype and small focal co ncentrations of spermatogenesis. Testicular biopsies from azoospermic men w ere immunohistochemically) evaluated for RBM expression. RBM expression was detectable in spermatogonia, spermatocytes, and round spermatids in biopsi es of men with obstructive azoospermia and normal spermatogenesis. No speci fic cell staining was shown in cases of Sertoli-cell-only (SCO) syndrome. I n biopsies of patients,vith spermatogenic disorders, all the germ cells wer e stained up to and including the stage level of the arrest in spermatogene sis, This approach enabled identification of small focal concentrations of spermatogenesis in a biopsy previously classified as being SCO by hematoxyl in and eosin staining. Thus, RBM can be a useful immunohistochemical marker for the specific identification of germ cells and provide greater accuracy in the histopathologic evaluation of testicular biopsies. Copyright (C) 20 01 by W.B. Saunders Company.