CASE REPORT Ovarian teratoma in an equine fetus: a case report

An eight-year-old Mangalarga Marchador recipient mare weighing 450 kg presented with fetal dystocia. The dead fetus showed anterior longitudinal presentation and dorsal sacral position. The limbs were extended, but the fetus had a right lateral deviation of the head. Under epidural anesthesia (7 mL of 2% lidocaine, Xylestesin 2%, CristChemical and Pharmaceutical Products Ltda, Itapira, S~ Paulo, Brazil), the fetal posture was easily corrected by retropulsion. However, severe abdominal distention of the fetus blocked its passage through the birth canal. A blind puncture of the fetal abdomen released a large volume of brownish-colored liquid and allowed for the delivery of the fetus. A necropsy was immediately performed and on external examination, the fetus presented only a mammary gland intumescence. On internal examination, an intra-abdominal cystic mass approximately 18 cm in diameter was observed. The mass had an irregular contour and was located in the right ovary. Upon macroscopic analysis, the cystic structure presented a thick and highly vascularized wall and was filled with a lobulated solid mass with yellowish-colored content and plaque of a rocklike consistency (Figure 1(a) and 1(b)). The contra-lateral ovary revealed a blackened appearance. Tissue samples from the right and left ovaries were collected, formalin-fixed, and paraffin-embedded. Subse- quently, the four-micron-thick sections were either stained with hematoxylin and eosin (HE an exception was the diaminobenzidine chromogen, with which the sections were incubated for five minutes. The monoclonal antibod- ies that were used were pan-cytokeratin (1:100, clone AE1/AE3, DakoCytomation, Carpinteria, CA, USA) and vimentin (1:100, clone Vim 3B4, DakoCytomation, Carpinteria, CA, USA). The immunostains for cytokeratin and vimentin were evaluated by qualitative analysis, and tumor components were characterized as either negative or positive. Sections from equine tissues that had previously been determined to be positive for cytokeratin and vimentin were used as positive controls. Sections where normal serum (Ultra V Block, Labvision, Fremont, CA, USA) was used in lieu of the primary antibody served as negative controls. Histopathological analysis of the right ovary revealed