Classical and spermatocytic seminoma in the dog: histochemical and immunohistochemical findings.

In the light of earlier human studies, 43 canine tumours diagnosed as seminoma were examined histologically with haematoxylin and eosin and periodic acid-Schiff (PAS) stains, and immunohistochemically with a monoclonal antibody against human placental alkaline phosphatase (PLAP). Twenty tumours were positive for both PAS and PLAP and were therefore diagnosed as classical seminoma (SE). The other 23 tumours were negative for both PAS and PLAP and were therefore diagnosed as spermatocytic seminoma (SS). Tubules with carcinoma in situ (CIS) were present in the testicular parenchyma surrounding 15 SEs and nine SSs.