Metastatic Tumor in Pregnancy: Placental Germ Cell Tumor with Metastasis to the Foal

Placental neoplasia was observed in an otherwise healthy Quarter Horse mare; subsequently, the mare’s 52-day-old foal was examined because of hindlimb ataxia, urinary incontinence and abnormal raised lesions of the distal limbs. Clinical and biochemical findings were supportive of liver disease and lumbosacral injury. Ultrasonographic evaluation of the abdomen suggested a liver mass which was confirmed with computed tomography (CT) and determined to be neoplastic via histopathologic evaluation of a liver biopsy sample. Regions of lysis affecting both femurs and third metacarpal bones, and a complete oblique sagittal fracture through the body of the first sacral vertebra were present on CT. Supportive care was provided until CT confirmation of diffuse hepatic neoplasia and vertebral fracture. Necropsy revealed a large, multinodular mass within the liver and a pathologic fracture of the first sacral vertebral body. Histopathologic comparison between neoplastic cells examined from the placenta and foal confirmed metastases of a germ cell tumour. Placental tumours are rare in all species; however, when noted in horses, clinicians should be aware of the possibility of metastatic spread to the foal.