A case of bilateral seminoma in an aged Mallard duck (Anas platyrhynchos) i
s described. Both testes were enlarged, Histologically, the testes revealed
large irregular seminiferous tubules containing diffuse sheets of large ro
und, hyperchromatic neoplastic spermatogenic cells, Mitotic figures were se
en. The growth had spread diffusely in both testes with no normal tissue le
ft. Occurrence of bilateral seminoma without metastasis to other organs is
unusual.