Cranial vena cava syndrome in a dog with a brachial plexus malignant peripheral nerve sheath tumour.

CASE REPORT A 13-year-old intact male German Shepherd Dog was presented for left forelimb lameness of 6 weeks’ duration. Physical examination findings included left-sided Horner’s syndrome, pain and left forelimb muscle atrophy. Neurological examination revealed leftsided forelimb monoparesis, decreased proprioception and withdrawal reflex. A brachial plexus mass originating from the C7–T1 intervertebral space was detected on magnetic resonance imaging (MRI) of the cervicothoracic spine. The presumptive diagnosis was neurological lameness caused by a tumour of the brachial plexus. The owners declined medical treatment. Three months later, the dog was re-admitted with signs of cranial vena cava syndrome, including generalised oedema of the head, neck and forelimbs. Euthanasia was performed and at necropsy, a large, ovoid, well-circumscribed mass was found in the axillar region. The mass had engulfed the brachial plexus nerves and infiltrated the brachiocephalic vein and the intercostal muscles of the first three ribs. It had penetrated the thorax and compressed the anterior vena cava. The histopathological examination of the mass revealed a highly pleomorphic neoplastic cell population that occasionally showed an angiocentric growing pattern. The neoplastic cells were consistently positive for vimentin, occasionally positive for S-100 and negative for cytokeratin, desmin, smooth muscle actin, glial fibrillary acidic protein, factor VIII, CD3 and CD79, supporting the diagnosis of malignant peripheral nerve sheath tumour (MPNST). CONCLUSION MPNSTs rarely metastasise, but they are highly invasive locally. Prognosis of canine MPNST is poor because of frequent recurrence after surgical excision. To the authors’ knowledge, this is the first case of cranial vena cava syndrome caused by MPNST. [ABSTRACT FROM AUTHOR]