General Considerations

•types: neuronoma, neurolemmoma, Schwannoma, malignant Schwannoma, neurofibroma, and neurofibrosarcoma

•peripheral nerve sheath tumor is preferred Schwann cells are origin and all have similar biologic behaviour

•fibrous, osteoid, chondroid, myxoid, and squamous patterns may be observed due to tumor differentiation

•peripheral nerve sheath tumor commonly involve nerve roots of the brachial plexus

•tumor progression occurs proximally and distally and may involve the spinal cord

•metastatic disease is rare although pulmonary metastasis has been reported

Peripheral Nerve Sheath Tumor Classification

•peripheral nerve sheath tumor classified according to level of involvement as:

•peripheral: tumor involvement distal to brachial or lumbrosacral plexus

•plexus: tumor involvement of nerves in brachial or lumbrosacral plexus and spinal nerves distal to intervertebral foramina

•root: tumor involvement of ventral or dorsal nerve roots or tumor entering intervertebral foramina

Clinical Features

•clinical signs are slowly progressive

•lameness (77%) and muscle atrophy (93%) are common with pain and palpable mass other findings

Diagnosis

•clinical signs and physical examination

•advanced imaging using CT and MRI provides an indication of level of involvement and associated changes

•myelography recommended for suspected spinal nerve root involvement

•EMG useful in delineating nerve root involvement

•CSF rarely useful

Treatment

•surgical treatment is recommended with technique depending on location:

•local resection

•amputation

•laminectomy

•combination of these procedures

Prognosis

•prognosis depends on level of involvement and ability for complete surgical resection

•excellent prognosis for peripheral classification of peripheral nerve sheath tumors due to ability for complete resection with no death related to tumor

•poor prognosis for plexus and root peripheral nerve sheath tumors with death due to tumor in 78%

•no significant differences between plexus and root groups although trend for plexus tumors to survive longer