Ultrastructure of gonadoblastoma and disgerminoma (seminoma) in a patient with XY gonadal dysgenesis.

The gross and fine morphology of gonadoblastoma and disgerminoma in a young phenotypic female with male karyotype and gonadal dysgenesis is described. Both the rudimentary gonads contain gonadoblastomas on the left side in association with a disgerminoma. In the light microscope the gonadoblastomas show peculiar hyaline masses, surrounded by Sertoli-like cells. In some areas a direct continuation between hyaline masses and basement membranes of round nests or large anomalous seminiferous tubules is obvious. At the ultrastructural level the hyaline masses consist of densely packed, largely concentric membranes closely similar to basement membranes or basal laminae of seminiferous tubules. These observations and the finding of transitional zones with gonadoblastoma elements in enlarged tubular structures suggest that gonadoblastomas originate inside tubules of dysgenetic testes. The peculiar hyaline masses with their concentric membranes might reflect hyperplasia and death of the Sertoli cells, each new generation of cells producing a basement membrane outside the preceding one.