Neurofibrosarcoma and Schwannoma
Schwannomas and neurofibrosarcomas are nerve sheath tumors, which means they involve the coating around nerve fibers that transmit messages to and from the brain and spinal cord (nervous system) and the rest of the body. Schwannomas are most often nonmalignant tumors. Neurofibrosarcomas are malignant tumors.
How Schwannomas and Neurofibrosarcomas Develop
Schwannomas form in the tissue that surrounds and insulates nerves. Schwannomas develop when schwann cells -- the cells that form the covering around nerve fibers -- grow abnormally.
Schwannomas typically develop along nerves of the head and neck. A type of schwannoma called vestibular schwannoma (or acoustic neuroma) affects the nerve that connects the brain to the inner ear, which can affect your sense of balance. Although schwannomas do not spread, they can grow large enough to press down on important structures in the brain (including the brain stem).
A very small percentage of nerve sheath tumors are malignant. These are known as malignant peripheral nerve sheath tumors, or neurofibrosarcomas.
Because neurofibrosarcoma originates in nerves, it is considered part of a group of cancers called soft tissue sarcomas. Soft tissue sarcomas are uncommon. They make up less than 1% of all cancers diagnosed each year. Neurofibrosarcomas account for only a small number of these soft sarcomas.
Neurofibrosarcoma is usually found in the arms and legs. However, it also can affect the lower back, head, or neck.
Neurofibrosarcomas can spread along the nerves. They typically don't reach other organs, although they can spread to the lungs.
What Causes Nerve Sheath Tumors?
Doctors don't know what causes most schwannomas and neurofibrosarcomas. However, nerve sheath tumors are more common in people who have the inherited disorder, neurofibromatosis type 1 (previously known as von Recklinghausen disease).
Vestibular schwannomas are linked to neurofibromatosis type 2. Having a genetic disorder called schwannomatosis also can increase the risk for schwannomas. A small percentage of neurofibrosarcomas are related to past radiation exposure.
Nerve sheath tumors are usually diagnosed when people are between the ages of 30 and 50, although these diseases can sometimes affect children and elderly people.