Dysgerminoma is a malignant neoplasm, which arises from undifferentiated germ cells, are considered rare neoplasms in animals but most reported cases have been in dogs and should be considered as a differential diagnosis for ovarian tumors. The clinical presentation is nonspecific and may include fever, pyometra, vaginal discharge, vomiting and diarrhea. The objective of this abstract is to report a rare case of a dysgerminoma found incidentally during ovariohysterectomy in a bitch with dystocia. An adult mongrel bitch was presented with clinical signs of dystocia with history that it had received progestogens injections to prevent pregnancy. During surgical procedure it was observed that fetuses were already dead and a mass in left ovary topography with 12 x 7 x 6 cm (Figure 1), firm and had brown to gray color on the cut surface. Microscopically was observed in germ cells form a mantle of cells with a narrow layer of fibrous stroma. The population of cells had moderate pleomorphism with polygonal cells, round nuclei with 1 to 3 nucleoli and an average of 2 mitotic figures per field higher magnification (400 x), compatible with dysgerminoma (Figure 2). This is a rare report of normal pregnancy in a bitch concomitant a dysgerminoma.

Figure 1. Mass in left ovary topography with 12 x 7 x 6 cm (arrow) - dysgerminoma and gravid uterus in bitch

Figure 2. Ovary - dysgerminoma Invasion of cancer cells in ovarian tissue (arrows) with focal hemorrhage (star). Degenerate secondary oocyte (arrowhead) is observed near the neoformation (bar = 100 µm H.E.).