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Peripheral Nerve Sheath Tumors |  |
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Amputation neuromas
(traumatic neuromas) are non-neoplastic, disorganized proliferations of peripheral nerve parenchyma and stroma that form in response to amputation or traumatic injury. They are most commonly identified after tail docking in dogs or neurectomy in the distal extremities of horses. The most common clinical presentation is a young dog that continuously traumatizes its docked tail. In horses, such a lesion appears as a firm, often
painful swelling at a neurectomy surgery site. Excision is curative. |
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Neurofibromas and
neurofibrosarcomas
(perineuromas, neurilemmomas,
nerve sheath tumors, hemangiopericytomas, neurothekomas, schwannomas) are spindle-cell tumors that arise from the connective tissue components of the peripheral nerve. They are believed to arise from Schwann cells, but they could also arise from mesenchymal cells, which produce the nonmyelinated connective
tissues that surround the myelinated nerve fiber. In dogs, forms of this tumor can be virtually indistinguishable from hemangiopericytomas and may be the same tumor. |
| In dogs and cats, peripheral nerve sheath tumors of the skin are found in older animals. In cattle, they have a suspected genetic basis, may be multiple, can develop in both the young and old, and are generally an incidental finding at slaughter; they arise from the deep nerves of the thoracic wall and viscera, and cutaneous involvement is rare. Regardless of the species, these tumors appear as white, firm, nodules. Attachment to a peripheral nerve may occasionally be noted. Both
benign and intermediate-grade malignant variants are recognized. Benign tumors are most common in cattle in which, due to their indolent nature, treatment is optional; also, additional tumors often develop spontaneously at other sites over time. In dogs, cats, and horses, most are locally infiltrative but do not metastasize. Complete excision is the treatment of choice. Where margins are narrow or insufficient, followup radiation therapy may increase the tumor-free interval. |
