Mixed germ cell tumor in the placenta of an Arabian mare

Abstract

A 14 year old Arabian mare was confirmed pregnant at 14 days via transrectal ultrasonography. The fetal heartbeat was present at 45 days and again at 5 months gestation. At 9 months gestation, the mare was presented for thick, clear vaginal discharge. The mare had travelled as a show mare and was current on vaccinations. She previously delivered multiple foals with no complications. Upon physical examination, the mare was clinically normal. Temperature, heart rate, and respiratory rate were within normal limits. The fetus could not be palpated or detected by ultrasonography transrectally. The fetal heartbeat was visualized on transabdominal ultrasonography but was not recorded. The allantoic fluid contained hyperechoic flecks. Treatment for placentitis was instituted and included trimethoprim sulfamethoxazole tablets (9,600/1,920 mg orally twice daily), altrenogest (22 mg orally twice daily), and flunixin meglumine (400 mg IV twice daily).2 The vaginal discharge remained unchanged despite treatment. Five days after the initial examination, the fetus was aborted. The fetus appeared grossly normal for his gestational age. The mare retained the placenta overnight. The following morning, gentle traction was required to remove the placenta as a large mass was holding it within the cervix. After removal, multiple masses were noted on the placenta. The fetus and placenta were submitted for necropsy. The placental masses and additional lesions found in the fetus’ liver were confirmed to be a mixed germ cell tumor. Placental germ cell tumors rarely metastasize to the foal. Metastasis occurs by the placental germ cell tumor sending cells through the umbilical vein to the fetal liver.1 The mare was treated for two days after the abortion with uterine lavages and infusion. She was re-bred to a different stallion two months later and delivered a normal foal. This case represents a rare neoplasia as a cause for vaginal discharge and abortion.