Can You Get Cancer In Your Nerves?
The tumors of the nerves known as peripheral nerve tumors are growths in or near the nerves that are involved in electrical signal transmission from the brain to the rest of the body and vice versa.(1)
Most of the peripheral nerve sheath tumors are benign (schwannomas, neurofibromas, neurofibromatosis) and on occasions malignant. Schwann cells surround the axon. Schwannoma is a tumor of differentiated Schwann cells, while neurofibroma arises from a mixture of Schwann cells, perineural cells, fibroblasts, and trapped axons.(2)
Schwannoma (neurilemoma, neurinoma) an encapsulated slow-growing tumor, arising from Schwann cells of the nerve sheath, which develops eccentrically to the nerve fibers. It is usually a solitary tumor responsible for 5% of all benign soft tissue that occurs between 20-50 years of age. Its association with neurofibromatosis type 1 is very rare. Schwannomas can occur anywhere in the body, but common sites include head and neck, flexor surfaces of extremities, mediastinum, and retroperitoneal region. Pain and neurological symptoms are only noted in large lesions.(3)
The most common subtype of neurofibroma is localized neurofibroma accounting for about 90% of all the cases. It can be seen as solitary, diffuse, and plexiform subtypes; the diffuse and plexiform subtypes are associated with type 1 neurofibromatosis. Localized neurofibroma accounts for <5% of all benign soft tissue tumors and seen in individuals between 20-30 years of age. It is usually a slow-growing and painless mass. Neurofibromas are usually non-encapsulated and associated with the parent nerve and cannot be separated from normal nerve fibers.(3)
Plexiform neurofibroma is a subtype of neurofibroma and pathognomonic of type 1 neurofibromatosis. The risk of malignant transformation is around 8-12%. Plexiform neurofibroma can cause enlargement of the affected extremity, hypertrophy of bone, and redundant skin when it involves the entire limb.(3)
Intraneural perineurioma (localized hypertrophic neuropathy) is a rare neurogenic tumor. It is mostly seen in children and young adults. The most common sites are sciatic nerve, brachial plexus, ulnar, and radial nerve. It presents with symptoms of weakness, denervation edema, and atrophy of muscles.(3)
Neurofibromatosis is an autosomal dominant disorder and presents as type 1 or type 1 neurofibromatosis. Type 1 neurofibromatosis is also known as von Recklinghausen disease that is mapped to 17q12 or type 2 neurofibromatoses, known as bilateral acoustic neuroma/vestibular schwannoma that is mapped to chromosome 22. Von Recklinghausen disease presents with cutaneous and subcutaneous neurofibromas that may range from hundreds to thousands. Intracranial involvement may present as gliomas, hydrocephalus, schwannomas of cranial nerves, plexiform neurofibromas, vascular dysplasia, myelinopathy, and hematomas. It can involve the spine, musculoskeletal system, and gastrointestinal tract. It can lead to seizures, optic and acoustic involvement, malignancies, endocrine disorders, hypertension, oral pathology, and osseous defects. Type 1 neurofibromatosis usually involves the eighth cranial nerve that can lead to nerve palsy, tinnitus, ataxia, hearing loss, vertigo, and can even be asymptomatic when small.
Malignant peripheral nerve sheath tumors include malignant schwannoma, neurogenic sarcoma, neurofibrosarcoma, which arise from a nerve or neurofibroma and demonstrate neural differentiation. They are responsible for about 5-10% of all soft tissue sarcomas. 25-50% cases of malignant peripheral nerve sheath tumors are associated with type 1 neurofibromatosis in which half of the lesions develop de novo and other half develop from malignant transformation of pre-existing neurofibromas.
These lesions present as painful, enlarging mass along with neurological symptoms. They are commonly seen between 20-50 years of age. They are more commonly found in the proximal portion of lower and upper extremities and trunk region and are associated with larger nerves. The prognosis of malignant peripheral nerve sheath tumors is very poor due to increased local recurrence and distant metastases. Furthermore, large tumor size and association with type 1 neurofibromatosis are independent markers of poor prognosis.(3)
Other malignancies that directly arise from nerves are lymphoma and chloroma; however, they are very rare. Lymphomas can be seen secondary to non-Hodgkin’s lymphoma, whereas chloroma (granulocytic sarcoma) usually presents due to leukemic relapse. They commonly affect the sciatic nerve.(3)