Tumors of almost any type can form along peripheral nerves. Most commonly, these are entirely benign tumors that do not metastasize to other parts of the body. Generally slow growing, these tumors can form within the substance of the nerve itself, and cause the nerve to gradually expand. Untreated nerve tumors begin to compress the adjacent nerve fibers, causing nerve dysfunction. Patients may experience pain, numbness, and/or weakness in the distribution of the affected peripheral nerve.
In almost all cases surgical excision to obtain a diagnosis and to cure the tumor is indicated. It is important to have an experienced peripheral nerve surgeon perform this operation, as most peripheral nerve tumors form within the nerve itself, and thus are surrounded and intertwined with functional nerve fibers that must at all costs be preserved during removal of the tumor.
In very few cases, the tumor is so involved with the peripheral nerve that complete excision is impossible without sacrificing the nerve. Generally your peripheral nerve surgeon will be able to tell from your MRI scan whether this is likely to be the case before the surgery is performed.
Malignant peripheral nerve tumors are rare, but do occur. There is often no way to tell for sure pre-operatively if a tumor is malignant. Pathological analysis of tumor tissue obtained via open surgery is the only way to know for sure if a tumor is malignant.
Some physicians (who are invariably not peripheral nerve surgeons) are tempted to perform needle biopsies of nerve tumors. This unfortunate procedure often not only fails to obtain diagnostic tissue, it almost uniformly damages the normal nerve fibers that surround the nerve tumor tissue. Thus, the procedure is not only useless, but it can cause irreparable weakness, numbness, and horrific neuropathic pain.
These are benign, slow growing nerve tumors that can occur anywhere in the peripheral nervous system. Generally patients discover a painless, firm lump. Though these tumors form within nerves and are surrounded by normal nerve fibers, they are easily separated from the nerve and removed by an experienced peripheral nerve surgeon.
These are the most common nerve tumors operated on by non-peripheral nerve surgeons. Tragically, these patients undergo a “lymph node biopsy,” only to awaken with permanent weakness, numbness, and pain, only to find to the horror of patient and surgeon that they indeed had a nerve tumor instead.
These are benign, slow-growing nerve tumors, similar to schwannomas. They commonly occur in patients who suffer from neurofibromatosis, a genetic disorder resulting in multiple tumors throughout the body.They can occasionally occur in patients without this genetic abnormality.
Cutaneous neurofibromas grow along small branches of nerves under the skin of patients with neurofibromatosis. They may present as painful lumps under the skin. They are not associated with large nerves, and are easily removed.
Malignant Peripheral Nerve Sheath Tumors
These include cancers that arise within peripheral nerves as well as plexiform neurofibromas that start out as benign tumors but then subsequently become cancerous. Nerve cancers are generally rapidly-growing and painful. It is important to operate on these lesions in a timely fashion before they have a chance to spread to other parts of the body. Once they metastasize, they are typically rapidly lethal. Goals of surgery for malignant nerve tumors are to obtain a tissue diagnosis, but not to necessarily remove the tumor. Although this seems counterintuitive to many people, attempting to remove the malignant tumor in the same fashion as removing a benign nerve tumore is essentially impossible. That is because cancer cells, invisible to the surgeons eyes, have already spread along the course of the affected nerve, even before the surgery is performed. Therefore just removing the tumor that the surgeon can see and feel will always leave some of the cancer behind.
Once these tumors are diagnosed by an open biopsy, a cure generally requires either limb amputation or at least removal of the entire adjacent nerve and all of the surrounding tissues, including muscle, blood vessels, and fat. Sometimes radiation and/or chemotherapy can be helpful, depending upon the exact type of tumor it turns out to be.