Schwannomas are benign tumors that arise from the nerve sheath. All peripheral nerve fibres have Schwann cells, and the tumor can occur on any nerve that has a schwann cell sheath.
Peripheral nerve schwannomas can be completely removed surgically, without injury to the nerve, since the abnormal growth does not include nerve fibres. The figure below depicts a schwannoma:
Usually there are no symptoms occuring with a schwannoma, however if the nerve fibres are displaced or abnormally compressed by the schwannoma the patient may notice some numbness or loss of function.
Neurofibromas may occur as a solitary nerve tumor, usually noticed as a localised mass under the skin. They differ from schwannomas in that the neurofibroma is intimately associated with the nerve fibres running through it.
Consequently, there will often be some form of neurologic abnormality present in the case of a neurofibroma; excision of the tumor, if it involves a peripheral nerve, may result in the loss of nerve function. The figure below illustrates how the tumor integrates with the nerve fibers:
A nerve may also contain mulitple Neurofibromas, in which case the surgeon has to consider the possibility of a disease known as Neurofibromatosis.
Neurofibromatosis, a genetic disease associated with the peripheral or central nervous system, is characterized by multiple tumors that have a tendency to be malignant.