Evidence of interepithelial seminoma spread into the rete testis by immunostaining of paraffin sections with antibodies against cytokeratin and vimentin.

Seminomas are tumors of high proliferative activity and show a marked tendency towards local invasion with the capacity for interepithelial spread within the seminiferous tubules as well as into the rete ductules. Immunohistologic investigations were carried out on paraffin sections of 47 typical seminomas. Immunostaining with antibodies against cytokeratin and vimentin allows the convenient detection of even small rete residuals in cases of subtotal rete destruction as well as the identification of discrete interepithelial seminoma spread within the rete ductules, thus facilitating seminoma staging.