Case description: A 7-year-old 42-kg (92.4-lb) sexually intact nulliparous female Italian Mastiff was examined because of a history of vaginal prolapse during diestrus.
Clinical findings: A physical examination revealed vaginal fold prolapse. Abdominal ultrasonography revealed an enlarged uterus with hypoechogenic content, corpora lutea in the ovaries, and a cyst in the right ovary. Hematologic abnormalities included leukocytosis, neutrophilia, mild anemia, and low Hct. Progesterone and estradiol concentrations were 9.36 ng/mL and 30.42 pg/mL, respectively, in serum and 72.72 ng/mL and 792 pg/mL, respectively, in the ovarian cystic fluid.
Treatment and outcome: Ovariohysterectomy was performed; the prolapsed tissue was repositioned by external manipulation and maintained in situ by temporary apposition of the vulvar lips with a retention suture. Anatomic and histologic examinations of the excised tissues revealed pyometra and papillary cystadenocarcinoma in the right ovary. The vaginal hyperplasia completely regressed at 35 days after surgery; 5 months after surgery, the dog's general condition was considered good.
Clinical relevance: Findings in this case were indicative of a hormonally active ovarian papillary cystadenocarcinoma in a female dog in diestrus. Hormone production by the cystadenocarcinoma was the predisposing factor that induced pyometra, mucosal hyperplasia, and vaginal fold prolapse in the dog. On the basis of these concurrent disorders, ovariohysterectomy was an appropriate treatment.