Plexiform neurofibroma of the cheek mucosa. A case report

GÓMEZ-OLIVEIRA G, FERNÁNDEZ-ALBA-LUENGO J, MARTÍN-SASTRE R, PATIÑO-SEIJAS B, LÓPEZ-CEDRÚN-CEMBRANOS JL. PLEXIFORM NEUROFIBROMA OF THE CHEEK MUCOSA. A CASE REPORT. MED ORAL 2004;9:263-7.

SUMMARY

The case reported deals with a solitary plexiform neurofibroma affecting the cheek submucosa.
Neurofibroma is an uncommon tumor which rarely appears in oral cavity but it represents the most common neurogenic tumor. Furthermore, plexiform variety is less frequent. Clinically, oral neurofibromas usually apperars as anodyne and asintomatic lesions. Sometimes, they produce nervous compression. In this case, tumor is big but asintomatic. There is no definitive radiologic image. It has association with poliglandular syndroms and phacomatosis. The treatment of choice is excision. There are doubts of the surgical results so that some authors are looking for new non-surgical treatments. The clinical characteristics, epidemiology, diagnosis and treatment are described as soon as a bibliographic revision

Key words: Plexiform neurofibroma, neurofibromatosis, benign tumor, phacomatosis, Von Recklinghausen

INTRODUCTION

Plexiform neurofibromas are benign proliferations arising from the peripheral nerves (1-7) and represent one of the most common neurogenic tumors (7,8). They arise from Schwann cells and perineural fibroblasts (3,6,7,9).

Neurofibromas can be multiple (1-4,6-8,10) or solitary. First ones are usually seen in the context of neurofibromatosis (7,8,10,11) and so, suggest this disease. Solitary ones are uncommon and they can be associated or not with neurofibromatosis (2,3,8).

Solitary neurofibromas rarely appear at the oral cavity, in spite of that, the most frequent location is the tongue, although they may occur at any site, specially on the palate, cheek mucosa, floor of mouth and even, intraosseous at the mandible (2-4,7)

Clinically, oral neurofibromas usually appear as pediculated or sessile nodule, with slow growth, affecting skin or mucosa (2,3,6,7). Therefore, differential diagnosis must be established with other similar lesions as papilomes, fibrous hyperplasias and schwannomas (2,12)

Pain and paresthesia are the most common symptoms as a result of nervous compression (4).

There are two histologically forms: plexiform and myxoid (2,3). The latter is the most common, while the other is uncommon (9) and can be associated with poliglandular syndromes ((MEN III) (13) and von Recklinghausen's disease.

The treatment of choice is surgical excision, although authors like Gupta and cols, are trying a new therapy based on the use of thalidomide in symptomatic patients with plexiform neurofibromas (14), due to doubts of the surgical results.

CASE PRESENTATION

A 67-years old woman is examined at our service with the main complaint of a mass located in left cheek mucosa. The lesion appeared two years before and no symptoms were associated with it except for its big size which was decreasing.

Personal history includes: knee's prothesis, colecistectomy and umbilical herniorraphy.

Intraoral examination disclosed the presence of two lesions of 2 or 3 cm, mobile, well-delimited and elastic consistent, which had relationship neither each other nor parotid.

It is been performed preoperative FNAB which suggested pleomorfic adenoma from salivary gland. The next step was to perform a MRI due to the caractheristics and location of the mass. It showed a lesion located at the soft tissue of the left cheek, with homogeneus signal, hipointense at T1 and hiperintense at T2 (Fig. 1). It infiltrated supraorbital rim, descended into the external rim of the masseter muscle as far as the oral cavity and ended at the external wall of the maxillary sinus. Under the presumptive diagnosis of limphangioma and when the preoperative studies were performed, surgical removal of the lesion under general anesthesia was carried out. The tumor has not adherences to adjacent areas so that it was excised completely by means of rome disecction. (Fig. 2). The final result showed a cystic and arrosariated tubular tumor of 2 x 7 cm (Fig. 3).

Macroscopic examination showed a well-delimited, elongated and cilindrical structure, of approximately 11 x 1,7 cm covered by a capsule full of prominet vessels and nervous bundles and with cilindrical structures beside. The tumor was composed of a proliferation of cells with eosinofile citoplasm, bad defined edges, fusiform and spindle cores, which were arranged in bundles. There were no images suggesting mitosis. The tumor showed dense and lax areas and some vessels. Definitive diagnosis was of plexiform neurofibroma.

There were neither clinical finding nor personal/familiar history suggesting neurofibromatosis type I or poliglandular syndrome MEN III (MEN IIb) so that the lesions seemed to be independent of these diseases.

At the present moment, the patient has no signs suggesting tumoral recurrence, two years after surgery.

DISCUSSION

Plexiform neurofibroma is a kind of mesenchymal tumor which derivates from the cells supporting peripheral nerves, such as Schwann cells and perineural fibroblasts (6). It is an uncommon tumor, although it is the most frequent neoplasm originating in peripheral nerves (7). This tumor is associated with von Recklinghausen disease and poliglandular syndrome MEN III, so that, its presence obliges to rule out these two entities (4) (Tables I y II)

It appears in the third decade of life although it may appears between 10 months and 70 years old (6). Youngest patients has more solitary forms than older ones (7).

There are authors thinking it is more frequent in females (6) but other ones think it is in males (10), anyway, the difference between sexs is minimal (6).

The most frequent location is the skin. On the other hand there is no consense about intraoral location because of several authors think it is uncommon (2-4) while other ones think it is common (7). In our case, lesion was placed at the cheek mucosa. This one and the tongue are considered the most frequent places intraorally (2-4,7). It is also been described, although in extremely rare occasions, intraosseous location at the mandible (2-4,7).

It usually appears as a nodular, well-defined, mobile and sesile mass with slow growth. It use to be painless. Anyway, there may exist pain or paresthesias, due to nervous compression (4,6)

Imaging techniques are not diagnostic. However, MRI gives more information about the limits and extension of the tumor than CT scan does. Neurofibromas appear as low or isointenses at T1 and high-intenses at T2 (Fig1), well-defined and homoge-neous consistence (6).

FNAB is not diagnostic. Definitive diagnosis rests upon histological study (6). Macroscopically it appears as a whitish consistent mass and shine surface (6). Microscopically the tumor is composed of a proliferation of spindle cells arranged in an irregular pattern. Stroma is composed of collagen fibers and mucoid masses (6). Small axons all over the tumoral tissue are demonstrated with silver staining (7). S-100 protein is demons-trated with inmunohistochemical techniques (6,9,17).

The treatment of choice is surgical excision of the solitary lesions, trying to conserve the nerve from which the tumor originates, although sometimes, it is unpossible due to the tumor infiltration, and the nerve has to be resected with the tumor (4,6). Spontaneus regression after puberty has been reported so that several authors recommend surgical excision after that age (2). Solitary neurofibroma may become malignant although it is extremely rare (12). Multiple neurofibromas and those associated with von Recklinghausen's disease or poliglandular syndrome MEN III may present sarcomatous degeneration in a 3 to 15 % of cases (4-6) . Those tumors which has been excised for several times may also become malignant (3,5,6).

Recurrence is rare (4), although there are authors suggesting a higher rate of recurrence at head and neck location (5,18).

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