Mixed atrophy of the testis (MAT), a frequent finding in biopsies of formerly cryptorchid and/or infertile patients, is defined as the synchronous occurrence of both seminiferous tubules containing germ cells and Sertoli cell only-tubules in variable proportions. In tubules containing germ cells, different types of abnormalities in spermatogenesis may be seen. The presence of adult spermatids in the biopsy, even in small numbers, correlates with successful spermatozoa retrieval for "in vitro" fertilization techniques. Currently, it is unknown whether precursor lesions of MAT can be identified in cryptorchid patients during childhood.
Eighteen formerly cryptorchid adults who had undergone testicular biopsies in childhood had a repeat testicular biopsy to evaluate infertility. In prepubertal biopsies, abnormalities of the testicular parenchyma were classified into types I (slight alterations), II (marked germinal hypoplasia), and III (severe germinal hypoplasia). In postpubertal biopsies, the percentage of tubules containing germ cells and Sertoli cell only-tubules were estimated, as well as the presence of complete spermatogenesis. Abnormalities in spermatogenesis were classified into lesions of the adluminal or basal compartments of seminiferous tubules.
Comparison between prepubertal and postpubertal biopsies revealed that most specimens developing from type III lesions presented with incomplete spermatogenesis (P<0.0001) and more severe lesions of the germinal epithelium (P=0.049).
Type III lesions correlated with MAT characteristics that confer a worse prognosis for in vitro fertilization. Thus, MAT characteristics may be predicted in prepubertal cryptorchid patients, allowing a fertility prognosis. The pathogenesis of these lesions, and their possible inclusion into the spectrum of the testicular dysgenesis syndrome, are discussed.