Histologic classification of undescended testes.

On the basis of testicular biopsy study in 203 patients and study of a second biopsy specimen from 27 of these patients, prepubertal undescended testes were classified into four categories according to the mean tubular diameter, the tubular fertility index, and the Sertoli cell index. Type I cases (testes with minimal lesions) were characterized by a normal mean tubular diameter and normal tubular fertility and Sertoli cell indexes or slight tubular hypoplasia. This group represented 26 per cent of the undescended testes. The corresponding lesions can be observed from two years of age onward and are probably acquired. After puberty normal spermatogenesis occurs. Type II cases (24 per cent of the undescended testes) included testes with marked germinal hypoplasia as well as slight or marked tubular hypoplasia and a normal Sertoli cell index. After puberty these testes develop a degree of marked hypospermatogenesis, maturation arrest, or Sertoli cells with only isolated spermatogonia and primary spermatocytes. In type III cases (testes with diffuse tubular hypoplasia) the mean tubular diameter and the tubular fertility and Sertoli cell index values were severely reduced. This group represented 33 per cent of the undescended testes, and after puberty most of them showed seminiferous tubules with exclusively adult Sertoli cells. Type IV testes (diffuse Sertoli cell hyperplasia) were associated with a nearly normal mean tubular diameter and variable tubular fertility index values and represented 17 per cent of all the undescended testes. After puberty Sertoli cells do not mature completely, and therefore in spite of the earlier tubular fertility index, the germinal cell line does not reach adult development. Although early orchiopexy prevents tubular fertility index and mean tubular diameter deterioration due to the noxious effects of temperature in type I testes, we believe that there is no such benefit in the other types. These patients may present only slight modifications in these indexes.