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Dr. Ajay Kumar.B
'Chithira',
Thampuram Road, 
North Beypore,
Calicut - 673 015,
Kerala State.
Tel. No. 0495 2415880
9447075102
Email :dr_ajaikumar@yahoo.com  


ABSTRACT 

Schwannomas are slow growing benign nerve sheath tumours. They are not commonly seen in the oral cavity and the tongue is the most common site of schwannomas found there. Here, we report a rare case of a tongue swelling, which was histopathologically diagnosed as schwannoma and discuss its clinical presentation, histological features and management.


KEY WORDS
Neural Tumour, Schwannoma, Tongue


INTRODUCTION 
Neurilemmoma or schwannoma is a benign tumour of ectodermal origin deriving from schwann cells. It is found in peripheral nerves, where neurons are invested by schwann's sheath. It is usually located in the soft tissues of the head and neck. The oral cavity is involved in the 2nd or 3rd decade, the tongue being the predominant site. We report a rare case of a schwannoma of tongue occurring in an 18-year old girl.

CASE REPORT 
An 18-year old girl presented with an otherwise asymptomatic slow growing swelling on the right side of tongue of 9 months duration. Examination revealed a smooth, firm, non-tender, swelling measuring 4 x 3cm on the right half of tongue at the junction of posterior 1/3rd and anterior 2/3rd. There was no cervical or submental lymph node enlargement. The haemotological and biochemical parameters were within normal limits. Fine needle aspiration cytology from the swelling was inconclusive. At surgery, the swelling could be removed in toto with ease, via a longitudinal incision made on the right lateral aspect of tongue. Gross examination revealed a nodular, greyish mass measuring 4 x 2.5 x 2 cm with glistening white cut surface showing haemorrhagic areas. Microscopy showed characteristic Antoni A and Antoni B areas with eosinophilic Verocay bodies. Mitotic figures were absent. Based on these findings a histopathological diagnosis of schwannoma of the tongue was made. The post-operative period was uneventful. 

DISCUSSION 
Neuilemmoma (syn. Schwannoma, Neurinoma, Perineural fibroblastoma) is a benign, encapsulated perineural tumour of neuroectodermal derivation that originates from the schwann cells of the neural sheath of motor and sensitive peripheral nerves; the etiology is still unknown(1). The tumour is normally solitary, smooth-surfaced, slow growing and generally asymptomatic1. It may occasionally cause pain or discomfort(2). Multiple lesions may occur in the following clinical settings 

(i) multiple localized neurilemomas 
(ii) in association with neurofibroma in von Recklinghausen's disease 
(iii) in Schwannomatosis, a non-hereditary disease characterized by multiple subcutaneous and intradermal schwannomas together with tumours of internal organs. 

It may develop at any age(1) but is more common during the 2nd and 3rd decades of life(2). There is no gender predilection(1). 

Schwannomas are usually located in the head and neck region but intraoral development is quite uncommon(1). In this area in a decreasing order of frequency, the mobile position of the tongue, the palate, the cheek mucosa, the lip and gingiva are the locations(1). In the tongue, the tip is the least affected part(3). Although they account for just over 1% of benign tumours reported in the oral cavity(3), they are the most commonly encountered nerve sheath tumours here(2). Other common sites include the flexor surface of upper and lower extremities and less often the mediastinum and retroperitoneum.

Although Schwannomas originate from the nerve tissue, a direct relation with a nerve can be demonstrated only in 50% of cases.(1) They often arise from the 8th cranial nerve.(4) Other nerves commonly affected are the spinal roots, cervical sympathetic, vagus, peroneal and ulnar nerves(.)5 Tumours arising from the small nerves are freely mobile but mobility is restricted along the long axis in those arising from large nerves.(5) Pain and neurological symptoms are uncommon unless the tumours are large.5 They may occasionally wax and wane in size due to fluctuation in the amount of cystic change.(5) Deep neurilemmomas are usually symptomatic; those occuring in the posterior mediastinum may originate from or extend into vertebral canal forming a dumbbell tumour, which causes profound neurological symptoms.(5)

Grossly, Schwannomas are surrounded by a true capsule consisting of epineurium.(5) Cut surface reveals smooth, glistening, pink, grey-white or yellowish surface. There may be cystic areas and foci of haemorrhage and calcification. They are usually less than 5cm in size. Mediastinal and retroperitoneal schwannomas are larger with more cysts and calcification. Histologically, they are characterized by presence of alternating Antoni A and Antoni B areas.(5) Antoni A area is a highly ordered cellular component and consists of Schwann cells arranged in compact, twisted bundles, associated with delicate reticulin fibres and spindle-shaped nuclei aligned in parallel rows forming a typical palisading pattern. Between the rows there are fine cytoplasmic fibrils with acellular, eosinophilic masses called Verocay bodies.(1) Antoni B area is less cellular and is formed by irregularly arranged masses of elongated cells and fibres, similar in appearance to neurofibroma, with areas of cystic degeneration and edema.(1) Immunohistochemically, schwannomas show an intense and relatively uniform staining for S-100 protein, which is a marker for Schwann cells.(5) The cells also express Vimentin, Leu 7 antigen and glial fibrillary acidic proteins (GFAP).(6)

In the differential diagnosis one must consider neurofibroma, granular cell tumours, lipoma, fibroma, leiomyoma and adenoma.(3) Isolated Schwannomas hardly ever become malignant.(3,4) Treatment is always surgical and usually requires only an excision or enucleation of the tumour, with no local or locoregional prophylactic measures3. Schwannomas do not recur if the excision is complete.(3,4)

REFERENCES
1. Chiapasco M, Ronchi P, Scola G. Neurilemmoma (Schwannoma) of the oral cavity: A report of 2 clinical cases. Minerva Stomatol. 1993 Apr; 42(4):173-8.
2. Krolls SO, McGinnis JP Jr, Quon D. Multinodular versus plexiform neurilemmoma of the hard palate - Report of a case. Oral Surg Oral Med Oral Pathol. 1994 Feb; 77(2):154-7.
3. Gallesio C, Berrone S. Schwannoma located in the tongue - A clinical case report. Minerva Stomatol. 1992 Dec; 41(12):583-90.
4. Dreher A, Gutmann R, Grevers G. Extracranial schwannoma of the ENT region. Review of the literature with a case report of benign schwannoma of the base of the tongue. HNO. 1997 Jun; 45(6):468-71.
5. Enzinger FM, Weiss SW.: Benign Tumors of Peripheral Nerves, in Enzinger FM, Weiss SW (Eds): Soft Tissue Tumors. 3rd Edition, Mosby-Year Book,Inc., Missouri,1995, pp 821-888.
6. Lopez JI, Ballestin C. Intraoral Schwannoma. A clinicopathologic and immunohistochemical study of nine cases. Arch Anat Cytol Pathol. 1993; 41(1):18-23.



LEGENDS

Fig1. Schwannoma of tongue.


Fig2. Enucleation of the tumor.

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