Solitary submucous neurofibroma of the mandible: review of the literature and report of a rare case

Neurogenic tumors are rare in the oral cavity, particularly so when malignant. Traumatic neuroma, although usually included with neurogenic tumors, is a reactive process rather than a true neoplasm [1]. In contrast, neurofibroma and schwannoma derive from nerve fibers, the perineurium, the endoneurium and the neurolemmomal cells [1]. Neurofibromas may present either as solitary lesions or as part of the generalised syndrome of neurofibromatosis or von Recklinghausen's disease of the skin [4–8]. Since the first description of solitary neurofibroma (neurilemmoma, schwannoma) of the oral cavity in 1954 by Bruce only few cases have been reported in the literature [2].

Although neurofibroma represents one of the most common neurogenic tumors it is an uncommon intraoral tumor [3] like some other intraoral tumours [4]. Neurofibromas can be multiple or solitary. The tumor's most frequent location is the skin and its multiple appearance is highly associated with von Recklinghausen's disease and poliglandular syndrome MEN III [5–9]. It mainly appears in the third decade of life although occurrence between 10 months and 70 years old has been described. Any preference of sex is reported contradictorily [6]. There are no correlations reported with immunocompromising diseases [10].

Clinically, oral neurofibromas usually appear as pediculated or sessile nodule, with slow growth. They are usually painless, but pain or paresthesia may occur due to nervous compression. The most frequent location is the tongue, although they may occur at any site, especially on the palate, cheek mucosa and floor of the mouth [1, 11–14]. Even intraosseous location of the mandible has been described [15–18]. The definitive diagnosis is due to histological examination.

The macroscopic appearance of the oral neurofibroma is characterized by a whitish consistent mass with shiny surface. Microscopically the tumor is composed of an irregular pattern of proliferative spindle cells. The stroma is composed of collagen fibers and mucoid masses. Small axons all over the tumoral tissue are demonstrated with silver staining. Neurofibromas are immunopositive for the S-100 protein in 85 to 100% of the cases, indicating its neural origin [19–23].

Treatment of choice is surgical excision of the solitary lesions, trying to conserve the nerve from which the tumor originates [5]. Malignant transformation of solitary neurofibroma is extremely rare. Recurrence is also rare although some authors suggest higher rate of recurrence at head and neck location of solitary neurofibromas [24–28]. Therefore, the prognosis is quite excellent.

A 64-year-old male patient with a history of somewhat alcohol but no nicotine or any other diseases attended the department for Cranio- and Maxillofacial Surgery. Clinical examination revealed an exophytic tumor in the oral cavity extending all along the lingual aspect of the left mandible (fig. 1). Panoramic radiographs showed little to moderate interdental loss of bone between teeth 37 and 38 but no other abnormalities. Several biopsies from the oral cavity revealed a submucous benign mesenchymale proliferation with no signs of malignancy and thus, the tumor was completely excised under general anaesthesia (fig. 2, fig. 3). Surgical treatment also included extraction of teeth 37 and 38 and a modelling osteotomie. Immunohistochemical findings showed a solitary submucous neurofibroma with a predominate fibromatous component (fig. 4).

In the presenting case the lesion occured at the lingual site of the left mandible presenting as painless pediculated exophytic tumor with slow growth. The localisation supports the lingual nerve as origin for the neurofibroma. The patient presented no signs of von Recklinghausen disease or poliglandular syndrome. Preoperative panoramic radiographs showed no serious abnormalities. Definitive diagnosis was based upon histological and inmunohistochemical findings. A clinical follow-up has been regularly performed for one year, there was no evidence of recurrence until now.

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.