Damage of Spermatogenesis

Abstract

To perform a thorough histologic analysis or to interpret an evaluation report, an understanding of the process of normal spermatogenesis is necessary. Spermatogenesis is regarded as normal when most of the tubules in a given section represent one or more of the six stages of spermatogenesis (I–VI). These stages of spermatogenesis are a characteristic association of germ cells and represent several waves of spermatogenesis occurring simultaneously within the seminiferous epithelium. In the human, a so-called multistage arrangement is found. The structural preservation of testicular tissue fixed with Bouin’s or Stieve’s solution and embedded in paraffin is adequate to identify all cell types. Furthermore, it allows the use of modern histologic techniques, such as immunohistochemistry (IHC) and in situ hybridization, to find evidence of gene expression on the protein and mRNA levels, such as the correct histone–protamine exchange during spermiogenesis, the state of differentiation of Sertoli and peritubular cells and the proliferation pattern of spermatogonia. If the seminiferous epithelium reveals a reduced number of elongated spermatids and defined stages of spermatogenesis cannot be identified, the term hypospermatogenesis should be applied. There are numerous defects, including multinuclear spermatids or spermatogonia and, most often, the occurrence of different spermatogenetic defects, such as maturation arrest at different levels (early round spermatids, primary spermatocytes, or spermatogonia), Sertoli cell–only syndrome, and the total loss of seminiferous epithelium, leaving only thickened lamina propria (tubular shadows) in the adjacent seminiferous tubules of a given section (mixed atrophy). Leydig cells may show a diffuse hyperplasia or focal nodular accumulation. Testicular intraepithelial neoplasia, which is known to be the precursor of seminomatous and nonseminomatous germ cell tumors—except for spermatocytic seminoma—may be recognized by its large size, clear cytoplasm, and large irregularly outlined nuclei with numerous nucleoli of the cells. The nature of these atypical spermatogonia must be determined by immunohistochemical staining of the membrane-bound placenta-like alkaline phosphatase (PLAP). The interstitial localization of these cells indicates an early invasive state of seminoma.