Abstract
Biopsies of testicular specimens taken from 41 patients that were diagnosed as having idiopathic Sertoli‐cell‐only syndrome were classified into two types, A and B, on the basis of histological and immunohistochemical findings. Thirty eight specimens that were classified as type A exhibited seminiferous tubules of small diameter and with tubular wall hyalinization, but containing normal adult type Sertoli cells. The other three specimens that were classified as type B showed no seminiferous tubular wall hyalinization, and their Sertoli cells had vimentin distribution localized in the subnuclear cytoplasm and had a pseudostratified lining, features resembling the appearance of fetal Sertoli cells. In one patient with a seminoma, a comparative study of the same testis prior to and post‐irradiation was undertaken. Judging from this, postpubertal depletion of the germ cell population was considered to be responsible for the tubular atrophy observed in type A. Type B testes, though small in number, were characterized by a morphology distinct from the type A, but their pathogenesis remains unknown.