Benign Peripheral Nerve Tumors

Types

Most peripheral nerve tumors are benign. They affect nerves either directly (by growing within them) or indirectly (by pressing against them).

Neurofibroma

This type of peripheral nerve tumor most commonly develops in individuals who have neurofibromatosis. Neurofibromatosis type 1 (NF1) occurs in about 1 in 4,000 people in the United States. The vast majority of patients with NF1 have mild symptoms from neurofibromas. These patients, however, can develop other conditions and related symptoms, such as severe scoliosis (curvature of the spine), enlargement or deformity of bones other than the spine and a tumor on the eye nerve (optic glioma).

Schwannoma

Schwannomas are the most common type of peripheral nerve tumor in adults. They are nonmalignant. Usually schwannomas are isolated lesions, except when they are associated with neurofibromatosis type 2 (NF2) or schwannomatosis.

Schwannomas typically arise from a single fascicle (a bundle within the main nerve) and displace rather than invade the rest of the nerve. When schwannomas enlarge, more fascicles are involved, making removal more difficult.

Schwannomas may occur anywhere. In general, they grow slowly. Most patients with schwannomas in the limbs may notice a new mass and may experience some symptoms, especially if the mass is bumped accidentally.

Vestibular schwannomas occur near the brain stem and cerebellum and press on nerves that control balance. Patients with vestibular schwannomas may have difficulties with balance or hearing problems. Read related details about acoustic neuroma.

Neurofibromatosis type 2 (NF2)

Patients with this condition may develop tumors on both sides of the brain. Symptoms include progressive hearing loss, poor balance, headaches, facial pain or numbness. If the tumors are not treated and continue to grow, NF2 can affect nearby nerves, including the brain stem, and cause death.

Dumbbell Tumors

Dumbell tumor

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These rare schwannomas or neurofibromas often grow to resemble a large dumbbell based on the bony confines that shape their growth and extension. They may occur in the spine (and extend out the natural openings in the spinal canal) or in the lower abdomen near the hip (the sciatic notch), and extend from the pelvis to the abdomen.

Dumbbell tumors are often considered inoperable because they are so intertwined with important nerves. Mayo surgeons have a broad base of experience in successfully removing these challenging tumors.

In a report in the Journal of Neurosurgery, Mayo surgeons described how high-resolution MRI helps them identify cases in which the sciatic notch tumors displace rather than directly involve the sciatic nerve. At Mayo, these tumors can be safely removed by teams of colon and rectal surgeons, urologists and neurosurgeons.

Lipoma

Lipomas are benign, soft lumps under the skin caused by slow-growing fat cells. They usually appear on the neck, shoulders, back or arms, most often in people age 40 to 60 years. In most cases they do not cause pain or other problems, but they should be examined and monitored through regular checkups. Lipomas that occur near nerves may compress them.

Ganglion Cysts

Ganglion cysts most commonly form from joints, such as the wrist or the base of a finger. The lump can cause pain and interfere with use of a limb. Ganglion cysts can occur elsewhere and compress neighboring nerves. In those cases, the lump should be surgically removed.

While some ganglion cysts form as a result of an injury, most cysts have no known cause. The cysts can increase or decrease in size. Some ganglion cysts go away without medical treatment. Read more about treatment of ganglion cysts.