Cervical extradural mast cell tumour in a 2-year-old Irish Sport Horse colt.

A 2-year-old Irish Sport Horse colt presented with acute, severe and rapidly progressive neurological signs, arriving recumbent to the hospital. Ante-mortem diagnostics did not reveal the cause of the recumbency, and the colt was euthanized after treatment and supportive care did not result in clinical improvement. A cranial cervical extradural mast cell tumour with eosinophilic granulomas and secondary compressive myelopathy with axonal degeneration was diagnosed on post-mortem evaluation. No other masses or clinically relevant findings were present, suggesting a primary neoplasm. Neoplasia associated with the spinal cord is rare in horses, and often carries a grave prognosis due to diagnostic and treatment barriers based on the large size of the patient.