Diagnosis and surgical management of an extraskeletal osteosarcoma of the brachial plexus in a Belgian shepherd dog

An 11‐year‐old Belgian shepherd presented with progressive right thoracic limb lameness. Computed tomography and magnetic resonance imaging revealed a brachial plexus neoplasm and cytology was suggestive of a sarcoma. The patient underwent forequarter amputation and hemilaminectomy of the fifth cervical to first thoracic vertebrae with nerve root transection. Histopathology confirmed extraskeletal osteosarcoma. Twelve months post‐operatively, the dog was exercising normally, and computed tomography did not identify local recurrence or metastatic disease. This is the first recorded case of canine brachial plexus extraskeletal osteosarcoma.