Multiple Undifferentiated Pleomorphic Sarcoma (Malignant Fibrous Histiocytoma) with Extradural Involvement in a 7-Year-Old Labrador Retriever.

A 7-year-old castrated male Labrador retriever was referred for evaluation of progressive hind limb paresis of 4 weeks' duration. On computed tomography and magnetic resonance imaging examination, masses were found in several regions including the lung, right kidney, and peritoneum. Additionally, an extradural mass at the region of T13-L1 was identified, which is assumed to related to the chief complaint, progressive hind limb paresis. With the consent of the owner, a dorsal laminectomy was performed to remove the mass and surrounding tissues for the palliation of the hind limb paresis. Hematoxylin and eosin staining and immunohistochemical examination revealed the mass to be consistent with an undifferentiated (high-grade) pleomorphic sarcoma. The patient presented with recurrence of the hind limb paresis, respiratory discomfort, and urinary incontinence. The owner declined treatment and the dog was euthanized. Systemic metastasis was confirmed on postmortem microscopic examination. To the authors' knowledge, this is the first report describing multiple undifferentiated high-grade pleomorphic sarcoma with extradural involvement developing into the vertebral canal through the intervertebral space, resulting in spinal damage, in a dog.