A diagnosis of an unusual lower lip swelling: Schwannoma

Sneha Upadhyay; Jyoti Bhavthankar; Mandakini Mandale; Jayanti Humbe

doi:10.4103/npmj.npmj_121_17

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CASE REPORT

Year : 2017 | Volume : 24 | Issue : 3 | Page : 191-193

A diagnosis of an unusual lower lip swelling: Schwannoma

Sneha Upadhyay, Jyoti Bhavthankar, Mandakini Mandale, Jayanti Humbe
Department of Oral Pathology and Microbiology, Government Dental College and Hospital, Aurangabad, Maharashtra, India

Date of Web Publication

30-Oct-2017

Correspondence Address:
Sneha Upadhyay
Department of Oral Pathology and Microbiology, Government Dental College and Hospital, Aurangabad, Maharashtra
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/npmj.npmj_121_17

Abstract

Schwannoma is a benign tumour of Schwann cell origin. Although it commonly occurs in the head and neck region, its intraoral presentation is rare. Establishing a clinical diagnosis of schwannoma is often difficult due to its non-specific clinical features. Hence, histopathological telltale features of Antoni A and Antoni B areas are unexpected in most cases. Reported here is a case of intraoral schwannoma affecting a 17-year-old male who presented with a slow growing mass in the lower lip.

Keywords: Antoni A, Antoni B, intraoral schwannoma, lower lip, Verocay bodies

How to cite this article:
Upadhyay S, Bhavthankar J, Mandale M, Humbe J. A diagnosis of an unusual lower lip swelling: Schwannoma. Niger Postgrad Med J 2017;24:191-3

How to cite this URL:
Upadhyay S, Bhavthankar J, Mandale M, Humbe J. A diagnosis of an unusual lower lip swelling: Schwannoma. Niger Postgrad Med J [serial online] 2017 [cited 2022 May 28];24:191-3. Available from: https://www.npmj.org/text.asp?2017/24/3/191/217398

Introduction

Schwannoma, also called as neurilemmoma, perineural fibroblastoma, Schwann cell tumour and lemmoma, is a benign nerve sheath tumour derived from Schwann cells. Initially described as 'neurinoma' by Verocay in 1910, this entity is subject to frequent misdiagnosis clinically.^[1] It is usually seen as a solitary lesion. However, cases of multiple schwannomas may be seen in association with neurofibromatosis Type 2.^[2],[3] Most intra-oral schwannomas have been reported in association with the tongue; it is therefore generally not included in the differential diagnosis of a lower lip swelling.^[4],[5],[6] Lower lip swellings are usually thought to be a mucocele, fibroma, salivary gland tumour or even haemangioma. Since the surgical treatment and prognosis depends on the diagnosis, correct diagnosis is not negotiable. Clinicopathologic correlation must be done to avoid this. Reported here is a case of schwannoma in a 17-year-old male occurring on the lower lip, thus necessitating the inclusion of schwannoma in the differential diagnosis of lower lip swelling.

Case Report

A 17-year-old male reported with a painless swelling on the left side of the lower lip to the Department of Oral Pathology and Microbiology, Government Dental College and Hospital, Aurangabad, on 4^th July 2016. The patient had first noticed the swelling 2 years prior to presentation and it had progressively enlarged in size. He had also suffered a trauma 14 years prior to presentation which had resulted in laceration of the lower lip and mobility of the anterior teeth. The healing was uneventful according to the patient. On physical examination, a 3.5 cm × 1.5 cm, non-tender, oval mass was palpable on the left side of the lower lip with normal-appearing overlying mucosa. The soft-to-firm mass was not attached to the adjacent structures and hence was mobile [Figure 1]. Digital pressure did not elicit pain. The provisional clinical diagnosis considered was benign lesion.

Figure 1: 3.5 cm × 1.5 cm, non-tender, oval soft-tissue swelling seen on the left side of the lower lip. The overlying mucosa was normal in appearance. The mass was not attached to the adjacent structures

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Laboratory investigations such as complete blood count, bleeding time and clotting time were requested by the surgeon before excision. These results of these tests were within the normal limits. A high-frequency ultrasonography revealed a heteroechoic solid lesion in the lower lip on the left side with few vascular channels and no calcifications. A provisional diagnosis of mesenchymal tumour was considered. The overlying mucosa was reflected and complete excision of the lesion was done under local anaesthesia. Grossly, the lesion was an encapsulated mass measuring 2.5 cm × 2 cm with a greyish white smooth surface [Figure 2]. On gross examination, due to its encapsulated nature, location and colour, the differential diagnoses considered were traumatic fibroma, lipoma, dermoid cyst, schwannoma and salivary gland neoplasm. On 1-week follow-up, suture removal was done. The healing of the operation site was uneventful.

Figure 2: The gross specimen was 2.5 cm × 2 cm. The cut surface is homogeneous in consistency and yellowish white

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Microscopically, uniformly encapsulated mass with areas of streaming fascicles of Schwann cells exhibiting a palisaded arrangement around a central acellular eosinophilic area was suggestive of Antoni A type arrangement. The other parts of the tissue were relatively less organised and cellular with spindle cells randomly arranged within a loose myxomatous stroma, suggestive of Antoni B type arrangement. Some areas of cystic degeneration and haemorrhage were also apparent [Figure 3]. [Figure 4] shows Verocay bodies, Antoni A and B patterns. Thus, the final diagnosis of schwannoma was made.

Figure 3: Photomicrograph showing typical arrangement of cells in Antoni A (yellow) and Antoni B (black) patterns (H and E, ×100)

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Figure 4: Photomicrograph with higher magnification showing Antoni A (yellow), Verocay bodies (white) and Antoni B (black) patterns (H and E, ×400)

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Discussion

Schwannoma is a rare benign neural sheath tumour arising from Schwann cells of neurilemma or neural sheath of peripheral, cranial or autonomic nerves. Schwann cells form an insulating membrane, myelin sheath around larger fibres to enhance nerve conductance. Schwannomas arise when proliferating Schwann cells form a tumour mass encompassing motor or sensory peripheral nerves.^[3] Cranial nerves I and II lack Schwann cells and hence do not give rise to schwannoma.^[4]

Schwannomas are rare as supported by many authors.^{[7],[8],[9],[10]} Do Nascimento stated that these tumours represent 0.04% of all intraoral lesions.^[8] Leu and Chang in their review of 52 cases of schwannomas originating in the head-and-neck region area found only seven of these cases. The lesions were located, one in hard palate, one in soft palate, two in submasseteric, one in tongue and one in the lower lip.^[10] Two types have been written about in the literature depending on the location: central and peripheral.^[9]

Histologically, the tumour tissue consists of the so-called Antoni A and B type arrangement. Type A areas show densely packed, elongated spindle cells with nuclear palisading around central acellular eosinophilic areas representing Verocay bodies formed by thin cytoplasmic fibres and reduplicated basement membrane while type B tissue has a more myxoid consistency and haphazardly arranged spindle-shaped cells.^[1] The term 'ancient schwannoma' is employed when histologically degenerative changes such as haemorrhage, hemosiderin deposits, inflammation, fibrosis and nuclear atypia are seen. Nodular growth pattern is observed in 'plexiform schwannoma.'^[8]

Schwannoma is a slow-growing painless encapsulated tumour which is usually of long duration at the time of presentation. As the lesion grows, the nerve may be pushed to one side and does not become a part of the tumour.^[8],[10] Pressure on adjacent nerves produces pain.^[1] Approximately 9%–14% of malignant schwannomas occur in the head and neck, which may cause pain, hoarseness, dysphagia, cranial nerve neuropathies and even Horner syndrome.^[11] It is believed to arise from the proliferation of Schwann cells at one point inside the perineurium.^[12] In this case, schwannoma may have arisen from an end branch of the mental branch of cranial nerve VII.^[13]

Wolff et al. found mutations in the NF2 gene at position 22q12.2 as the basis of schwannoma formation both in sporadic schwannomas and in neurofibromatosis Type 2. NF2 is a tumour suppressor gene that codes for merlin (schwannomin), a cell membrane-associated protein that links the cell membrane and the cytoskeleton and functions in intracellular signalling pathways. Its decreased synthesis causes a disturbance of growth arrest through cell–cell contact.^[14]

Clinical differential diagnosis includes lipomas, haemangiomas, epidermoid and dermoid cysts, granular cell tumour and lymphangioma.^[15] The typical histopathological features and immunohistochemistry findings such as positivity for S100 are used to exclude other diagnoses.^[4] Lipomas are rare in the oral cavity and have superficial miniscule blood vessels.^[3] Granular cell tumour, a differential diagnosis of tongue swellings, is characterised by large cells with granular cytoplasm and overlying pseudoepitheliomatous hyperplasia.

Haemangiomas can be ruled out using diascopy. Mucocele appears fluctuant and bluish due to the presence of free mucin. Lymphangiomas on palpation produce a crepitant sound as lymphatic fluid is pushed from one area to another. Dermoid cysts are doughy on palpation due to sebum and show epithelium and secondary skin structures.^[2]

Schwannomas might be confused with neurofibromas. The latter are unencapsulated, originating from a mixed cell population that includes Schwann cells. Schwannomas present as freely moveable mass while neurofibromas are centripetal, irregular and lobulated masses fixed to the adjacent structures with adult predominance.^[3],[11] The latter are difficult to excise, recur or at least persist after incomplete excision and can transform into a malignancy in hereditary neurofibromatosis.^[15] Computed tomographic (CT) findings could help distinguish between schwannoma and odontogenic cysts or tumours in intraosseous lesions.^[12] The treatment for benign schwannoma consists of total surgical excision of the lesion. The recurrences as well as the malignant transformation are rare events.^[9]

Imaging modalities such as CT or magnetic resonance imaging can aid the diagnosis, displaying a homogeneous, very well-defined solid lesion. However, the definitive diagnosis requires histological study.^[8]

Conclusion

Presentation of schwannoma at an unusual location such as the lower labial mucosa demands its inclusion in the differential diagnosis of asymptomatic circumscribed nodule or mass. However, clinicopathologic correlation is a key. Treatment should be aimed at complete resection of the tumour, preserving the nearby structures. The prognosis is excellent.^[12]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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9.	Handschel J, Heikaus S, Depprich R, Kübler NR, Yekta SS, Smeets R, et al. Intraoral schwannoma: Review of the literature and presentation of a rare case. Cranio 2012;30:150-3. [PUBMED]
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15.	Sardinha SD, Paza AO, Vargas PA, Moreira RW, Moraes M. Schwannoma of the oral cavity. Histological and immunohistochemical features. Braz J Oral Sci 2015;4:806-9.

Figures

[Figure 1], [Figure 2], [Figure 3], [Figure 4]

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