Bilateral Dysgerminoma and Cystic Endometrial Hyperplasia with Pyometra in a Bitch

Background: Ovarian tumors are considered rare both in dogs and cats. Germ cell neoplasms correspond to approximately 15% of the cases and can be classified into dysgerminomas, teratomas and teratocarcinomas. Reports of bilateral dysgerminoma in dogs and cats are rare. The aim of this work was to describe a case of bilateral dysgerminoma and cystic endometrial hyperplasia with pyometra in a bitch by presenting the clinical, surgical, pathological and immunohistochemical findings. Case: A 10-year-old female crossbred dog was presented with a history of vomiting, apathy and purulent vulvar discharge. Physical examination revealed hyperthermia and pain was observed on abdominal palpation. Ultrasound examination revealed cystic formation and increased echogenicity inside the uterus. The animal underwent ovariohysterectomy (OHE). Macroscopically, the ovaries were multinodular, spherical to ovoid in shape, measuring 6 cm in diameter, and with a dark red color; they exhibited a firm consistency and a hemorrhagic cut surface with cystic areas and foci of necrotic tissue. At microscopic evaluation of both ovaries, the neoplasm consisted of large and polyhedral cells with amphophilic cytoplasm which were arranged in cords separated by connective tissue. The cells exhibited an anaplastic appearance, with central nuclei, large amounts of granular chromatin and one or more evident nucleoli. Several mitotic figures, often incomplete and with consequent formation of multinucleated cells similar to giant cells, were observed. Immunohistochemical detection of cytokeratin and vimentin was performed for further examination. The ovarian tumor exhibited positive staining for cytokeratin and negative staining for vimentin. Discussion: Most ovarian tumors are asymptomatic and many times are considered incidental findings during spaying surgeries. On physical examination, affected animals may show palpable abdominal masses, ascites and systemic signs caused by hormonal disturbances. The macroscopic and microscopic findings seen in this case are in accordance with those found in the literature and confirm the diagnosis of bilateral dysgerminoma and cystic endometrial hyperplasia-pyometra. Dysgerminoma should be differentiated from other neoplasias as lymphosarcoma, solid adenocarcinoma, solid granulosa cell tumor, theca cell tumor and teratoma. Diagnosis is performed by histopathological analysis. Immunohistochemistry can be performed to identify the origin of tumoral cells in order to assist the differential diagnosis for other neoplasias. Even though the immunohistochemical result can be positive for cytokeratin, this is not considered usual for dysgerminomas. The positive result for cytokeratin is related to the anaplastic characteristic of the tumor. Most cases of dysgerminomas are described in older dogs and cats, yet it can develop in younger animals. Dysgerminoma is a tumor that is typically unilateral and is hardly ever found in both ovaries. The rarity with which this neoplasia is observed in bitches can be related to the premature age at which OHE is performed.