Abstract
An 11-year-old, 35 kg, castrated male Labrador retriever expressed acroparalysis and dysstasia. A mass involving the medulla spinalis through the foramina nervosa between the 5th and 6th cervical vertebrae was found by MRI examination. At necropsy, there was a translucent white cartilage-like mass (1.5×2.5cm) in the epineurium of the right 6th cervical nerve. The mass was present in the epidural layer of spinal canal, and compressed the 5th cervical cord. The neoplastic tissue had a lobular structure and cartilageous matrix. The tumor cells had swollen nuclei, differences in size, binuclear cells, and rare mitotic figures. Immunohistochemically, the cytoplasms and nuclei of the tumor cells were consistently positive for S-100 protein. This tumor was thought to have derived from pluripotent undifferentiated mesenchymal cells in the epineurium of the right 6th cervical nerve, with a diagnosis of extraskeletal chondrosarcoma. Extraskeletal chondrosarcomas are extremely rare in both human and domestic animals.
