Ovarian dysgerminoma in a bitch.

A nine year old Terrier-Chihuahua crossbred bitch was presented to the Western College of Veterinary Medicine with a history of anorexia, vomiting and diarrhea. A palpably enlarged uterus and purulent vaginal discharge were found on physical examination. Pyometra was diagnosed and ovariohysterectomy was subsequently performed. One ovary was twice the size of the other, firm and mottled grey-white on the cut surface. A dysgerminoma involving the larger ovary was diagnosed on histological examination. This tumor, closely resembling the male seminoma, was characterized by a uniform population of large round cells with scant acidophilic cytoplasm, frequent mitotic figures and focal aggregates of lymphocytes. History and clinical signs were considered to relate to the pyometra rather than the dysgerminoma. No conclusions could be made regarding hormonal elaboration by the tumor because sex hormone levels were not measured. Two years following discharge the dog was reported to be well.