A neurofibroma is a benign, slow-growing nerve sheath tumor, 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.
Larger neurofibromas tend to grow along larger, more important nerves. Unlike schwannomas, however, they are more intimately intertwined with the nerve fibers, making removal more difficult. Nevertheless, with meticulous surgical technique, these difficult tumors may be safely removed, causing few if any deficits.
When a neurofibroma involves a particularly long segment of nerve or nerves, it is called a plexiform neurofibroma. These are generally impossible to remove without removing the entire nerve, necessarily causing a major neurological deficit. Therefore, these variants are not usually subjected to surgery.
A small percentage of plexiform neurofibromas change from benign to malignant, and can spread to other parts of the body. These cancers are almost uniformly lethal without aggressive treatment. If a plexiform neurofibroma becomes exceptionally painful and/or begins to rapidly expand, suggestive of cancerous transformation, it must be definitively treated.
There are two types of neurofibromatosis, type 1 and type 2. Type 1 also known as Recklinghausen’s disease affects 1 in every 3,000 people, and cases are typically mild with limited amounts of tumors. Type 2 affects 1 in every 25,000 people.
Common Symptoms of Neurofibroma
Symptoms for type 1 vary depending on the patient. If small skin nerves are involved lesions may appear as small bumps. If large nerves are affected elephantiasis (enlargement of affected body parts) may occur.
Diagnosis of Neurofibroma
To properly diagnosis neurofibromatosis type 1 two or more of the following must hold true:
- Two or more neurofibromas
- Six or more brownish discolorations on the skin
- Bigger than 5mm in diameter in pre-adolescents
- Greater than 15 mm in diameter in adolescents/adults
- Freckling in the armpit/groin area
- Two or more small masses on the iris of the eye
- Bone lesions (sphenoid dysplasia)
- Optic glioma
- First degree relative with neurofibromatosis type 1
The proper diagnosis of neurofibromatosis type 2 requires either of the following:
- Eighth cranial nerve masses on both sides
- Immediate relative with neurofibromatosis type 2, and either an eighth nerve mass on one side or two of the following: meningioma, glioma, schwannoma, or neurofibroma
Treatment Options for Neurofibroma
Typically neurofibromas do not need to be surgically removed. Depending on the type of diagnosis, pain, progressive neurological complications, compression of tissues in close proximity, and possibility of a malignant tumor, surgical exploration and excision may be considered. Neurofibromas that occur under the skin can be painful, and occur on surfaces subject to pressure. Typically these types of neurofibromas can be removed without creating a neurological deficit.