eMedicine Specialties > Dermatology > Diseases of the Oral Mucosa
Oral Neurofibroma
Updated: Aug 30, 2007
Introduction
Background
Neurofibroma is an uncommon benign tumor of the oral cavity derived from the cells that constitute the nerve sheath. Neurofibroma is seen either as a solitary lesion or as part of the generalized syndrome of neurofibromatosis (usually neurofibromatosis type 1 [NF-1], also called von Recklinghausen disease of the skin). The solitary form does not differ from the disseminated form or the multiple form of the disease, except that systemic and hereditary factors present in the disseminated form are absent in the solitary type.
Oral cavity involvement by a solitary and peripheral plexiform neurofibroma in patients with no other signs of neurofibromatosis is uncommon. Sporadic cases have been reported in the submandibular gland, tongue, and on the periosteum at the mental foramen. This sporadic syndromic occurrence has also been seen in the cutaneous region, and several authors have suggested that these isolated neurofibromas may represent a hamartomatous growth.
Pathophysiology
The cell of origin for neurofibroma has not been definitively identified. Some believe it arises from the Schwann cell. Perineural fibroblasts are neuroectodermal tissue cells that synthesize collagen and create a network that envelops the individual axis cylinders of the nerves with their associated Schwann cells. Some investigators believe that perineural fibroblasts give rise to the neurofibroma.
The cause of solitary neurofibroma is unknown. However, neurofibromatosis is inherited as an autosomal dominant trait with a high degree of penetrance but variable expressivity. As many as 50% of cases are reported to be the result of spontaneous mutation. Recently, 2 subsets have been defined: one is associated with the neurofibromatosis type 1 (NF1) gene, and the other is associated with the neurofibromatosis type 2 (NF2) gene.
Frequency
United States
Little information is available regarding the relative frequency of solitary oral neurofibromas and oral manifestations of neurofibromatosis. A survey of series on oral neurofibromas has reported that approximately 20-60% of cases are associated with neurofibromatosis. Intraoral neurofibromas may be seen in as many as 25% of patients with neurofibromatosis. Another review of head and neck neurofibromas reported that approximately 25% of all neurofibromas are seen in the head and neck region and 6.5% occur in the oral cavity as solitary or multiple lesions associated with NF-1.
Although these lesions may be seen anywhere in the oral cavity, the most common location of this tumor is the tongue. They have also been described on the gingiva, palate, major salivary glands, and maxillary bones.
Mortality/Morbidity
Solitary neurofibromas have a good prognosis, with only rare instances of local recurrence after excision. However, in neurofibromatosis, a larger proportion of patients develop recurrence after excision, and multiple recurrences are associated with malignant transformation. Spontaneous malignant transformation of 1 or more lesions is also reported. The rate of transformation is estimated to be 5-15%. This neurofibrosarcomatous change has an extremely poor prognosis, and distant metastasis is common. The average 5-year survival rate is dismal and ranges around 10-15%. A study involving 66 cases of head and neck neurofibromas reported that no recurrence of the neurofibromas was detected after surgical removal in approximately 33% of the patients during follow-up ranging from 3-230 months.
Race
No racial predilection is recognized for oral neurofibromas.
Sex
No sexual predilection has been described for oral neurofibromas.
Age
The average age of patients presenting with solitary neurofibromas is approximately 45 years; however, for intraoral neurofibromas associated with neurofibromatosis, the lesions may present at any age, with no specific bias.
Clinical
History
- Patients usually present with an uninflamed, slowly enlarging, asymptomatic lesion that varies greatly in size from tiny nodules to large pendulous masses.
- The lesion is rarely painful; however, patients may experience pain if the lesion is secondarily traumatized due to its location, eg, on the tongue or on the hard palate.
Physical
- Presentation
- Oral neurofibromas usually present as submucosal, nontender, discrete masses that range in size from a few millimeters to several centimeters (see Media Files 1-2).
- The tumors tend to grow slowly, and patients are usually asymptomatic.
- Manifestations of neurofibromatosis specific to the oral cavity include enlarged fungiform papillae on the dorsum of the tongue and diffuse enlargement of the gingiva.
- In patients with mandibular involvement, enlargement of the inferior alveolar canal in the mandible and a flaring of the inferior alveolar foramen (the so-called blunderbuss foramen) have been reported.
- Oral manifestations may be seen in as many as 70% of patients with neurofibromatosis. Involvement of the trigeminal nerve may cause facial pain or paresthesia. Neurofibromatosis of the skin may present as multiple nodules or as a single pendulous mass.
- In patients with neurofibromatosis, extensive destruction of alveolar bone, mimicking periodontal bone loss, has been reported. This may be confused with routine periodontitis or other systemic disease. Owing to the potential systemic and genetic implications, the diagnosis of oral neurofibroma requires referral to the appropriate medical specialist to rule out the association with neurofibromatosis.
- The tongue, the buccal mucosa, and the vestibular areas are the most common sites of presentation.
- Rare cases of diffuse unilateral enlargement of gingiva have been reported in association with neurofibromatosis. In a recent case report, an 8-year-old child presented with gingival enlargement around all teeth of the right side of both jaws. This may resemble drug-induced gingival enlargement or gingival fibromatosis.
- Occasional cases of neurofibroma located centrally within the jaw have been reported. These intraosseous lesions may exhibit large sizes with a considerable expansion potential (see Media File 2).
Causes
The cause of these lesions is unknown; however, neurofibromatosis syndrome or the disseminated form is inherited as an autosomal dominant trait and may present with a variety of lesions, including a highly variable number of neurofibromas.
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| References |
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References
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Further Reading
Keywords
neurofibromatosis, von Recklinghausen's disease of the skin, von Recklinghausen disease, fibroma molluscum
