Neurofibroma and Neurofibromatosis


The nerves that come from the spinal cord and extend into our trunk and extremities are called peripheral nerves. A benign soft tissue tumor that forms from the nerve tissue of the peripheral nerve is called a neurofibroma. A neurofibroma may be just is a single tumor, but more often a person has multiple tumors. The presence of multiple neurofibromas is associated with a genetic condition called neurofibromatosis.

Other terms used when describing neurofibromas are:

  Plexiform tumor - on any peripheral nerve; larger, irregular shape, can grow into the nerve more extensive, can become malignant1
  Dermal – on the nerves in the skin, can be cutaneous (on the surface of the skin), subcutaneous (just below the skin, deep nodular (under the lowest later of the skin)

Whether a single tumor (solitary tumor) or part of neurofibromatosis, a neurofibroma can vary in size. It can be a small mass when the tumor develops on a small cutaneous (skin) nerve or it cause enlargement of an extremity (as in elephantitis) when it’s on a larger nerve.

Neurofibroma and neurofibromatosis are considered aggressive benign conditions. The tumors can grow into the bone, weakening it and making it susceptible to fractures; they can also press on nerves and blood vessels causing neuropathy or loss of blood flow to area of the extremity.

There are two types of neurofibromatosis:

  Neurofibromatosis type 1 (von Recklinghausen’s disease) is a hereditary condition, meaning it’s passed from a parent to a child. It affects 1 in 3000 people ref.
  More common characteristics associated with type 1 are:

There is a small (7%) risk of a neurofibroma associated with neurofibromatosis type 1 becoming cancerous.1 The cancerous form of neurofibroma is called a neurofibrosarcoma.
  • Six or more café-au-lait spots (area of brown pigmentation on the skin)
  • Two or more neurofibromas
  • Freckling in the arm pits or groin area
  • Deformity of the bone that forms the eye socket
  • Associated tumors:
    o Benign tumors on the iris of the eye (Lisch nodules)
    o Cancerous tumor on the optic nerve to the eye (glioma)
    o Tumors of the adrenal gland, brain or spinal cord
  Neurofibromatosis type 2 is the more severe type and affects 1 in 50,000 people. It is also a hereditary condition.
  More common characteristics associated with type 2 are:
  • Benign tumors called acoustic neuromas on the vestibularcochlear nerve in the ears. Both ears are usually affected and this can lead to balance and hearing problems.
  • Tumors on the covering of the brain and spinal cord
  • Brain tumors called gliomas
  • Possibility of café-au-lait spots but usually less than with type 1
  • Increased risk of cataracts

Diagnosis of Neurofibroma and Neurofibromatosis

When a neurofibroma is suspected, an MRI is done to determine exactly where the tumor is located, its size, and if it is invading other tissues.

A biopsy is necessary to confirm the diagnosis of neurofibroma. The location and extent of the tumor will guide the physician in deciding the best type of biopsy.

Once the lesion is confirmed as a neurofibroma, a thorough medical history can help in determining the next steps in diagnostic testing. If there is a family history of neurofibromatosis, an extensive work up may be recommended to determine if the patient has a type of neurofibromatosis.

Treatment of Neurofibroma and Neurofibromatosis

“Watchful waiting” or active surveillance is usually recommended for neurofibromas that are not causing pain or weakness, or invading other structures. This involves regular (possibly yearly) imaging studies like an MRI to assure there hasn’t been a change in the size that would require surgical removal. If there are symptoms or if vital structures are being invaded, surgical excision is recommended. A surgeon with expertise in peripheral nerve surgery should be consulted for treatment. Because plexiform tumors are more invasive, they may be more difficult to remove without causing some damage to the nerve.

In extreme cases where neurofibromas have caused enlargement of extremities to the point that a person has lost functional abilities, amputation may be considered. This is usually done for self-care and hygiene but does not change the growth or development of other tumors.

There are clinical trials (research studies) available for treatment of neurofibromatosis. Patients with severe symptoms or more rapidly growing neurofibromas should discuss options with their treating physicians. Clinical trials focused on aspects of neurofibromatosis can be found at clinicaltrials.gov.


Reference:
Korf BR, Malignancy in Neurofibromatosis Type 1; The Oncologist, December 2000 vol. 5 no. 6 477-48

Korf BR, Plexiform neurofibromas; Am J Med Genet. 1999 Mar 26;89(1):31-7.