Clinical History

The Siberian husky, male, 13 years old, was brought to the Small animal clinic at Faculty of veterinary medicine in Belgrade, with incapability of standing on the thoracic left limb. The dog started limping on left thoracic limb one year ago, and lameness increased during time. A month ago, the dog stopped leaning on that limb (in case of leaning on that limb, it would show signs of pain). The dog started to drag the limb ten days ago, and the pain was increasing, and manifested with whining and biting its limb in the area of m. brachialis.

Physical and Neurologic Examination

Sensorimotor monoplegia with apparent muscles atrophy of the thoracic left limb with no other neurological abnormalities.

Diagnostic Testing

CBC and serum chemistry: no abnormalities; vertebral radiographs C6 - T2: no abnormalities; MRI without contrast: above the top of the left lobe of a lung parathrahealy, oval, clearly limited, expansive formation is noticeable, with the dimensions 43x57mm, which holds back the trachea contralateraly and pushes down the top of lungs. The tumor had moderate unhomogenous hyper signal in T1W, and distinctive hyper signal in T2W. The suspected diagnosis was neoplasia of brachial plexus peripheral nerves. Following euthanasia, histological examination confirmed infiltrative and poorly circumscribed tumorous mass, composed of a dense population of spindle-shaped cells arranged in fascicles, whorls or sheats. There were two to five mitotic figures per high-power field. Immunohistochemically, most spindle cells were positive for vimentin and negative for S-100, keratin and GFAP. Based on the morphological and immunohistochemical features, the tumour was classified as a malignant peripheral nerve sheath tumour (MPNST) with dominant mesenchymal component.