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An Official Publication of the Indian Association of Oral and Maxillofacial Pathologists


 
CASE REPORT Table of Contents   
Year : 2006  |  Volume : 10  |  Issue : 1  |  Page : 28-30
 

Plexiform neurofibroma of the gingiva: Report of a rare case


Dept.of Oral Pathology, Govt.Dental College, Trivandrum - 695011, India

Correspondence Address:
R Rajendran
Dept.of Oral Pathology, Govt.Dental College, Trivandrum - 695011
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0973-029X.37798

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   Abstract 

Plexiform neurofibromas are highly suggestive of neurofibromatosis type I, but they are not pathognomonic as claimed. Clinical and pathological features of a patient with solitary plexiform neurofibroma of the gingiva that manifested as a diffuse, unilateral enlargement are presented here. An excision biopsy of the lesion was performed, which underwent recurrence within six months period at the local site and assumed almost the same dimensions. The patient underwent excision again, this time extending to the uninvolved margins of the oral mucosa. The overlying mucosa was excised along with the tumour mass, allowing healing by secondary intention to take place. The patient remains uneventful after eight months of clinical follow-up. There are neither clinical findings nor personal/family history of neurofibromatosis type I or MEN III (MEN II b), so that the lesion seems to be independent of these syndromes. The gingival involvement is very rare and a perusal of English bibliography of this lesion could not reveal another report of its occurrence in the gingiva.


Keywords: Plexiform neurofibroma, gingiva, neurofibromatosis, MEN III (MEN lIb), NF-1, p53, p27- kipl


How to cite this article:
Rajendran R. Plexiform neurofibroma of the gingiva: Report of a rare case. J Oral Maxillofac Pathol 2006;10:28-30

How to cite this URL:
Rajendran R. Plexiform neurofibroma of the gingiva: Report of a rare case. J Oral Maxillofac Pathol [serial online] 2006 [cited 2019 Aug 22];10:28-30. Available from: http://www.jomfp.in/text.asp?2006/10/1/28/37798



   Introduction Top


Plexiform neurofibromas (PNFs) are benign proliferations arising from peripheral nerves [1]. They appear as either a solitary or as part of the generalized syndrome of neurofibromatosis (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 [2]. 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, two subsets have been defined: one is associated with the neurofibromatosis type 1 (NF I) gene and the other is associated with the neurofibromatosis type 2 (NF 2) gene [3]. Being the best defined Phakomatoses, it usually affects the skeletal system, central nervous system, eye, endocrine gland, and cardiovascular system. Gingival involvement is very rare. Clinical and pathological findings of a case of plexiform neurofibroma who had diffuse, unilateral gingival involvement, is presented here.

A survey of the published cases of oral neurofibromas has reported that approximately 20-60% of cases are associated with neurofibromatosis. Intraoral neurofibromas maybe seen in as many as 25% of patients with neurofibromatosis. Plexiform neurofibroma appears mostly in the third decade of life although it may appear between 10 months and 70 years of life [4]. It is equally distributed between sexes and the difference seem to be minimal. An informed appraisal of the demographic features of the plexiform neurofibroma of the gingiva seems impossible due to the exterme shortage of published case reports. The only one report of the lesion in the gingiva of which an English abstract was available was a Turkish article appeared in 2004 (Tani Girisim Radyol : 10; 39-43). No racial predilection is recognized for oral neurofibromas.


   Case Description and results Top


A 25-year-old male was examined at our services, with the complaint of a mass in the upper left buccal gingiva and contiguous alveolus, approximately since 8 years. The lesion appeared asymptomatic with no history of pain, tenderness, or discomfort except occasional episodes of bleeding upon provocation. The mass involved the marginal and attached gingiva, 2cm xl.5 cm in size extending from maxillary lateral incisor to first molar in same quadrant. No history of pathologic tooth mobility and / or altered sensation was reported over the affected mucosa. Radiological examination of the affected maxilla was noncontributory with no evidence of any lytic bone changes, widening of the periodontal ligament and/or cortical bone erosion noticed.

An excision biopsy of the lesion was performed 6 months back by raising a full thickness mucosal flap over the mass and the tumour was excised. The wound site underwent primary closure after inserting a plastic tube drain to minimize tissue tension and the healing was reported to be uneventful. When the patient turned up for follow up after a period of one month, the lesion appeared to have recurred at the same location and assumed almost the same dimensions. The patient underwent excision again, this time extending to the uninvolved margins of the oral mucosa and excising the overlying mucosa along with the tumour mass allowing secondary intention healing to take place [Figure - 1] (periodontal pack was given to cover the raw area). He remains uneventful after 3 months of postoperative follow up.

Macroscopic examination showed a well delimited, elongated, and fusiform mass confirming to its clinical size, partially covered by a capsule carrying prominent blood vessels, and nerve bundles and firm in consistency. Microscopically, the tumour mass consisted of grossly expanded nerves and nerve fibers which were largely replaced by neurofibromatosis tissue. These expanded nerves form thick, convoluted, cords and nodules macroscopically. The tumour cells were spindle shaped with fusiform or wavy nuclei found in a delicate connective tissue matrix: this matrix was partly myxoid in character [Figure - 2]. The lesion was partly circumscribed and seemed to blend in to the surrounding connective tissue. Mast cells were seen scattered throughout the lesion. Extensive interlacing masses of nerve tissue were supported by a collagen matrix. Small axons could be seen among the proliferating tumour cells. Here the biopsy was collected from the recurred lesion and the microscopic features reported were compatible with the former report of tissue procured during initial excision of the lesion.

There were neither clinical finding nor personal/family history suggesting neurofibromatosis type 1 or MEN III (MEN II) so that the lesion seemed to be independent of these diseases. Other lesions to be considered in the differential diagnosis include granular cell tumour, fibroma, scar tissue, neurilemmoma (Schwannoma), leiomyoma, rhabdomyoma, and other benign mesenchymal entities.


   Discussion Top


Plexiform neurofibroma is much less common than the ubiquitous conventional neurofibroma and takes two principal forms; a relatively small type lesion seen in the dermis or superficial subcutis; and a larger, usually deeply situated type, which often involves voluntary muscles or visceral structures. The anatomical distribution and depth of the lesion is very variable but the head and neck region is the most common site and involvement of superficial soft tissue is more frequent than deeper lesions. The involvement of oral mucosa is very rare and close perusal of English language literature on this lesion could not reveal another report of its occurrence in the gingiva. It is an important lesion for two reasons: first, at whatever site, it is pathognomonic of neurofibromatosis; secondly, it runs a small but significant risk of undergoing malignant change, particularly if deeply located [5]. The concept of plexiform neurofibroma being highly suggestive of neurofibromatosis type 1, had been contradicted by others who held that they are not pathognomonic as claimed [6]. Solitary plexiform neurofibromas may occur in patients without other stigmata ofNF-1, as it was in our case. The pathogenesis of such lesions is unclear, but they may result from mosaicisism of NF 1 or a related gene.

It usually appears as a nodular, well defined, mobile, and sessile mass with slow growth. The Intraoral locations reported earlier were that of buccal mucosa and tongue [4]. It is usually painless but there pain or paraesthesia due to nerve compression, may exist.

Imaging techniques are not diagnostic. However, MRI gives more information about the limits and extension of the tumour than CT scan does [4]. FNAB is not diagnostic. Definitive diagnosis rests upon histological study. Small axons all over the tumoural tissue are demonstrated with silver staining[7]. S-100 protein too had been demonstrated with immunohistochemical techniques [8].

The treatment of choice is surgical excision of the solitary lesion, trying to conserve the nerve from which the tumour originates, although sometimes it is impossible due to tumour infiltration, and the nerve has to be resected with the tumour. Spontaneous regression after puberty has been reported so that several authors recommend surgical excision after that age [4]. Early surgical intervention of small superficial PNF may thus be considered as a preventive strategy for later disfigurement, and function deficits. Trying to conserve the nerve from which the tumour originates is at many times impossible due to the tumour infiltration, and the nerve has to be resected with the tumour. The recurrence rate of this tumour varies in different reports. Some held it as rare while others have reported higher rate of recurrences. The clinical behavior of our reported case prompt us to speculate that recurrence is a problem with oral PNF, and should be reckon with while planning management strategies.

The prognosis for solitary neurofibroma is extremely good with rare instances of recurrence. However, 5-15% patients with neurofibromatosis, exhibit malignant transformation of at least one lesion. This neurofibrosarcomatous change has an extremely poor prognosis and distant metastasis is common. As benign plexiform neurofibromas can transform into malignant peripheral nerve sheath tumours, studies have focused on identifying co-operative genetic events that might be associated with malignant transformation [9]. Functional inactivation of several key cell cycle regulations, including p53, p27-kipl, and p16, have been identified in malignant transformation compared with their benign neurofibroma counterparts [10]. In support of this notion, two groups have demonstrated that mice with targeted mutations in the NF 1 and p53 genes developed malignant tumours when both the genes were inactivated [11].

 
   References Top

1.Allen CM, Miloro M(1997): Gingival lesion of recent onset in a patient with neurofibromatosis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 84:595.  Back to cited text no. 1    
2.Fisher D, Chu P, Mc Calmont T (1997): Solitary plexiform neurofibroma is not pathognomonic of von Recklinghausen neurofibromatosis: a report of a case, Int J Dermatol, 36: 435.  Back to cited text no. 2    
3.Geist JR, Gander DL, Stefanac SJ (1992): Oral manifestations of neurofibromatosis types I and II, Oral Surg Oral Med Oral Pathol, 73:376.  Back to cited text no. 3    
4.Val-Bernal JF, Figols J, Vazquez-Berquero A(1995): Cutaneous plexiform schwannoma associated with neurofibromatosis type I, Cancer, 76:1181.  Back to cited text no. 4    
5.Lin V, Daniel S, Forte V (2004): Is a plexiform neurofibroma pathognomonic of neurofibromatosis type l?, Laryngoscope, 114: 14 10.  Back to cited text no. 5    
6.6 Alatli C, Oner B, Unur M et al (1996): Solitary plexiform neurofibroma of the oral cavity: A case report, Int J Oral Maxillofac Surg, 25:379.  Back to cited text no. 6    
7.Neville WB, Damm DD, Allen CM, Bouquot JE (1995): Oral & Maxillofacial Pathology, (2nd ed.) Philadelphia, PA, WB Sounders, p 380.  Back to cited text no. 7    
8.Nagasaka T, Lia R, Sone M et al (2000): Glandural malignant peripheral nerve sheath tumour: an unusual case showing histologically malignant glands, Arch Pathol Lab Med, 124:1364.  Back to cited text no. 8    
9.Friedman JM, Gutmann DH, Mac Collin M et al (1999): Neurofibromatosis: phenotype, natural history, and pathogenesis, (3rd ed.) Baltimore, Johns Hopkins University Press.  Back to cited text no. 9    
10.Birindelli S, Perrone F, Oggionni M et al (2001): Rb and TP53 pathway alterations in sporadic and NF 1related malignant peripheral nerve sheath tumours, Lab Invest 81: 833.  Back to cited text no. 10    
11.Vogel KS. Kleese LJ, Velasco-Miguel S et al (1999): Mouse tumour model for neurofibromatosis type 1 Science, 286:2176.  Back to cited text no. 11    


    Figures

  [Figure - 1], [Figure - 2]



 

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