Peripheral Nerve Tumors

+ 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 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 signs are slowly progressive
Lameness (77%) and muscle atrophy (93%) are common with pain and palpable mass other findings

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

Surgical treatment is recommended with technique depending on location:

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