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 Table of Contents  
CASE REPORT
Year : 2015  |  Volume : 27  |  Issue : 3  |  Page : 484-487

Rare case of palatal schwannoma: Case report and review of literature


Department of Oral Medicine and Radiology, MNR Dental College and Hospital, Sangareddy, Telangana, India

Date of Submission04-Mar-2015
Date of Acceptance03-Nov-2015
Date of Web Publication25-Nov-2015

Correspondence Address:
Nishanth Gollamudi
Department of Oral Medicine and Radiology, MNR Dental College and Hospital, Sangareddy - 502 294, Telangana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-1363.170474

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   Abstract 

Schwannomas, also known as neurilemmoma, are benign, slow-growing nerve sheath tumors arising from Schwann cells. Approximately 25-40% of schwannomas occur in the head and neck region. However, schwannomas that present in the oral cavity are relatively rare, constituting around 1% of all described cases in the head and neck region. [1],[2] Here, we report a rare case of an intraoral schwannoma, in a 28-year-old male, with painless swelling located in the posterolateral aspect of the soft palate on the right side. Definitive diagnosis was obtained after histopathology examination. Surgical excision of the tumor was done with no complications or recurrences.

Keywords: Antoni type A, benign tumor, neurilemmoma, soft palate, Verocay bodies


How to cite this article:
Yaga US, Mengji AK, Besta R, Gollamudi N. Rare case of palatal schwannoma: Case report and review of literature. J Indian Acad Oral Med Radiol 2015;27:484-7

How to cite this URL:
Yaga US, Mengji AK, Besta R, Gollamudi N. Rare case of palatal schwannoma: Case report and review of literature. J Indian Acad Oral Med Radiol [serial online] 2015 [cited 2019 Oct 14];27:484-7. Available from: http://www.jiaomr.in/text.asp?2015/27/3/484/170474


   Introduction Top


Schwannoma, also known as neurilemmoma or neurinoma, is a rare, slow-growing, benign, encapsulated tumor arising from nerve sheath cells (Schwann cells) that comprise the myelin sheaths. [3] The literature search revealed 16,906 reports containing the word schwannoma. However, 1117 articles have been published on this benign lesion in the "head and neck" region, and search containing the word "intraoral schwannoma" showed only 29 cases. Of all these cases reported, the tongue was the common site of occurrence and few cases showed involvement of buccal mucosa and vestibule. [4] Although these benign tumors may affect any site of the body, in the head and neck region, the incidence is around 25-48%. [5] Intraoral occurrence of schwannomas is rare with an incidence of about only 1%. [6] The sites of occurrence are usually the tongue, palate, floor of mouth, buccal mucosa, and mandible in descending order of incidence. [7] Schwannomas involving soft tissues appear as a smooth swelling and are asymptomatic. Swelling is the most common symptom, followed by paresthesia. It may occur at any age, but the incidence is usually seen in the 25-55 year age group and has no sex predilection. [6],[8] Clinically, these benign lesions are generally misdiagnosed as other common benign lesions such as fibroma or pleomorphic adenoma or any other minor salivary gland neoplasm on account of their slow growth, and as mucus retention cyst or palatal abscess, due to their site of occurrence. Treatment for these benign lesions is surgical excision. Schwannomas do not show recurrence if completely excised. [9] Hereby, we report a case of a rare intraoral schwannoma in a young male in the posterolateral part of the soft palate, which is an unusual location for intraoral tumors. The tumor was misdiagnosed initially as minor salivary gland neoplasm, whose diagnosis was established upon histological findings. A review of literature is also presented.


   Case Report Top


A 28-year-old male patient reported to the outpatient Department of Oral medicine, Diagnosis, and Radiology with the chief complaint of swelling in the oral cavity since 1 year. History taking showed that the patient was asymptomatic 1 year ago and later he noticed a small nodule like growth that was initially of small size and gradually increased to attain the current size. However, patient had only mild discomfort on deglutition. His past medical and dental histories were insignificant.

Extraoral examination showed no significant signs with no palpable lymph nodes. However, intraoral examination revealed a solitary dome-shaped swelling of normal mucosal color seen posterior to the junction of hard and soft palate, extending anteroposteriorly from the mesial aspect of 16 to 2 cm posterior to the distal aspect of 18 and mediolaterally from the mid-palatine raphe to palatal marginal gingiva of the maxillary posterior teeth just crossing the midline, and measuring approximately 4 × 4 cm in size. The surface over the swelling was smooth with prominent vasculature without any ulceration and the swelling had ill-defined borders. On palpation, the swelling was non-tender, firm in consistency with no evidence of any discharge [Figure 1].
Figure 1: Intraoral swelling seen at the junction of hard and soft palate on the left side

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Based on the chief complaint, past history, and intraoral examination of the swelling, a working diagnosis of benign neoplasm of minor salivary gland of soft palate was made. Other benign lesions such as fibroma, pleomorphic adenoma of minor salivary gland, lipoma, neurofibroma, epidermoid and dermoid cysts were considered under differential diagnosis. Panoramic radiograph of the area of interest showed no significant changes. To further know the extensions in all planes, computed tomography (CT) was advised, which on axial section showed a 27 × 25 mm, well-circumscribed soft tissue density lesion in the soft palate on the right side and no enhancement on contrast administration, which was suggestive of a minor salivary gland neoplasm of the soft palate [Figure 2].
Figure 2: CT axial and sagittal sections show a 27 × 25 mm, well-circumscribed, soft tissue density lesion in the soft palate on the right side

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Fine needle aspiration cytology on multiple smears showed numerous fragments of stroma with interspersed spindle cells suggestive of pleomorphic adenoma or benign soft tissue lesion. Further correlation with histopathological examination was advised. All routine hematologic investigations conducted before surgery were within normal limits. Informed consent was obtained from the patient and surgical excision was done with no damage to adjacent vital structures. The excised specimen measuring 3 × 2.5 × 1 cm was a grayish white encaspular mass which showed cellular connective tissue stroma composed of spindle cells (Antoni A) and the spindle cells exhibited palisaded arrangement around eosinophilic areas (Verocay bodies). There was also presence of salivary gland acini along with moderate vascularity suggestive of a common schwannoma [Figure 3] and [Figure 4]. Primary impressions were made and palatal obturator was fabricated with heat-cured acrylic. Postoperative healing was uneventful and was followed by placement of palatal obturator over the surgical defect [Figure 5].
Figure 3: Histopathological picture depicting Verocay bodies with parallel stacks, Schwann cell nuclei, and centrally placed eosinophilic cytoplasm

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Figure 4: Pictomicrograph showing distinctive and better organized Antoni A pattern with the nuclei in palisading clusters

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Figure 5: Post-surgical defect and picture showing obturator in place

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   Discussion Top


Schwannoma, also known as neurilemmoma or neurinoma or perineural fibroblastoma, [10] is an uncommon, benign, encapsulated tumor which arises from the nerve sheath cells or the Schwann cells. The nomenclature of these cells is attributed to the famous German physiologist and cofounder of the cell theory, Theodor Schwann. [7] Verocay first described them as neurinoma in 1908. [11],[12] Schwannomas commonly arise from the spinal nerve roots and intracranial nerves of the face. Most commonly, they are seen in the form of vestibular schwannoma or acoustic neuroma, when they affect the VIII cranial nerve (vestibulocochlear nerve). [13]

Age and sex

Intraoral schwannomas of the jaw may occur at any age, but incidence is usually seen in the 25-55 year age group and has slight female predilection (female to male ratio is 1.6:1). [10]

Site

Schwannomas in the head and neck region contribute to only one-fourth of all extracranial schwannomas. The intraoral occurrence is extremely low (1%). Intraoral schwannomas show predilection for the tongue, followed by buccal mucosa, lip, palate, and gingiva. [14] Intraoral schwannomas usually range from 1.0 to 5.0 cm in diameter. The reported duration of these tumors ranges from 3 months to 5 years. [7] Schwannoma is a benign, slow growing, usually asymptomatic tumor that sometimes shows submucosal swelling. Sometimes, the mass presses down on the neighboring nerve and causes neurological changes or pain. Pain and paresthesia are not unusual for intrabony tumors. [10] In a review done by Leu and Chang, [15] out of 52 cases of head and neck schwannomas, 7 lesions were seen intraorally, which included one in the hard palate, one in the soft palate, two in submasseteric area, one in the tongue, and one in lower lip. [16] But in our case, the location was soft palate, which is still rarer. So, achieving an accurate preoperative working diagnosis was reasonably difficult and we initially assumed it to be a minor salivary gland neoplasm.

Radiographic features

Radiographically, intraosseous schwannomas appear as unilocular radiolucencies with very thin sclerotic border. Sometimes the neighboring teeth may show external root resorption and cortical expansion. [17],[18] Imaging modalities such as ultrasound, CT, and magnetic resonance imaging (MRI) may be useful in arriving at a diagnosis and for determination of tumor margins and the extent of infiltration into adjacent structures. As schwannoma is a soft tissue tumor, CT study shows no specific radiographic findings. However, MRI is very much helpful in visualizing the internal structure of the tumor. [10]

Histopathology

Microscopic picture of schwannoma is unique and usually characteristic. These lesions are masses usually surrounded by capsule of the perineurium. They are usually composed of two cellular patterns, namely Antoni A and Antoni B. Antoni A areas show compact spindle cells with twisted nuclei arranged in fascicles. Nuclear palisading and oval-shaped Verocay bodies (formed by nuclei and cell processes) are observed. However, Antoni B areas are less cellular and less organized, representing degenerated Antoni A areas, which show anastomosing areas of spindle cells arranged haphazardly within myxoid, hypocellular matrix. [10] Immunohistochemistry acts as an adjunct giving the definitive diagnosis of the tumor. All types of schwannomas show positivity with neural markers such as S-100 protein [19] and glial fibrillary acidic protein (GFAP) in many cases. [17] The pericapsular region of a schwannoma may contain CD34-positive cells. [20]

Treatment and prognosis

Schwannomas are usually well encapsulated, so the treatment of choice is surgical excision under local or general anesthesia depending on the position of the tumor. The non-encapsulated form requires a margin of normal tissue and careful separation from the involved nerve. [21],[22] As recurrence and malignant transformation of neurilemmoma are exceedingly rare, the prognosis is usually very good. [10] In the present case, the mass was well encapsulated and could be totally excised. The prognosis was good.


   Conclusion Top


In conclusion, a rare case of an intraoral schwannoma on the posterolateral aspect of soft palate, which was initially misdiagnosed as a minor salivary gland neoplasm, has been presented in this report. Intraoral schwannomas are very rare and not encountered in day-to-day and specialty practice. These lesions must be differentiated from other benign lesions of oral cavity. It is difficult to diagnose this tumor based on clinical appearance alone. The definitive diagnosis can only be made after correlating the clinical, radiographic, and histopathological findings. The treatment of choice is complete surgical excision, and recurrences and risk of malignant transformations of neurilemmomas are exceedingly rare.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Martins MD, Anunciato de Jesus L, Fernandes KP, Bussadori SK, Taghloubi SA, Martins MA. Intra-oral schwannoma: Case report and literature review. Indian J Dent Res 2009;20:121-5.  Back to cited text no. 1
[PUBMED]  Medknow Journal  
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Arda HN, Akdogan O, Arda N, Sarikaya Y. An unusual site for an intraoral schwannoma: A case report. Am J Otolaryngol 2003;24:348-50.  Back to cited text no. 2
    
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Sawhney R, Carron MA, Mathog RH. Tongue base schwannoma: Report, review, and unique surgical approach. Am J Otolaryngol 2008;29:119-22.  Back to cited text no. 3
    
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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.  Back to cited text no. 4
    
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Amir R, Altman KW, Zaheer S. Neurilemmoma of the hard palate. J Oral Maxillofac Surg 2002;60:1069-71.  Back to cited text no. 5
    
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Santos PP, Freitas VS, Pinto LP, Freitas Rde A, de Souza LB. Clinicopathologic analysis of 7 cases of oral schwannoma and review of the literature. Ann Diagn Pathol 2010;14:235-9.  Back to cited text no. 7
    
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Baranoviæ M, Macan D, Begoviæ EA, Luksic I, Brajdiæ D, Manojloviæ S. Schwannoma with secondary erosion of mandible: Case report with a review of the literature. Dentomaxillofac Radiol 2006;35:456-60.  Back to cited text no. 8
    
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López JI, Ballestin C. Intraoral schwannoma: A clinicopathologic and immunohistochemical study of nine cases. Arch Anat Cytol Pathol 1993;41:18-23.  Back to cited text no. 9
    
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Prasanna Kumar D, Meghashri K. Schwannoma of the hard palate: A case report and review of literature. J Adv Oral Res 2012;3:23-8.  Back to cited text no. 10
    
11.
Chiapasco M, Ronchi P, Scola G. Neurilemmoma (Schwannoma) of the oral cavity: A report of 2 clinical cases. Minerva Stomatol 1993;42:173-8.  Back to cited text no. 11
    
12.
Leu YS, Chang KC. Extracranial head and neck schwannomas: A review of 8 years experience. Acta Otolaryngol 2002;122: 435-7.  Back to cited text no. 12
    
13.
Enzinger FM, Weiss SW. Benign Tumors of Peripheral Nerves. Soft Tissue Tumors. 4 th ed. Mosby: St. Louis; 1995. p. 821-88.  Back to cited text no. 13
    
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Pfeifle R, Baur DA, Paulino A, Helman J. Schwannoma of the tongue: Report of 2 cases. J Oral Maxillofac Surg 2001; 59:802-4.  Back to cited text no. 14
    
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Yang SW, Lin CY. Schwannoma of the upper lip: Case report and literature review. Am J Otolaryngol 2003;24:351-4.  Back to cited text no. 15
    
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Patil K, Mahima V, Srikanth H, Saikrishna D. Central Schwannoma of mandible. J Oral Maxillofac Pathol 2009;13:23-6.  Back to cited text no. 16
[PUBMED]  Medknow Journal  
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Parhar S, Singh HP, Nayyar A, Manchanda AS. Intra-oral schwannoma - A case report. J Clin Diagn Res 2014;8:264-5.  Back to cited text no. 17
    
18.
Chi AC, Carey J, Muller S. Intraosseous schwannoma of the mandible: A case report and review of the literature. Oral Surg Oral Med Oral Path Oral Radiol Endod 2003;96:54-65.  Back to cited text no. 18
    
19.
Regezi AJ, Sciubba JJ, Jordan R. Connective tissue lesions. In: Regezi AJ, Sciubba JJ, Jordan R, editors. Oral Pathology: Clinical Pathologic Correlations. 5 th ed. St Louis, Missouri: Saunders; 2008. p. 170-2.  Back to cited text no. 19
    
20.
Folpe AL, Billings SD, McKenney JK, Walsh SV, Nusrat A, Weiss SW. Expression of claudin-1, a recently described tight junction-associated protein, distinguishes soft tissue perineurioma from potential mimics. Am J Surg Pathol 2002;26:1620-6.  Back to cited text no. 20
    
21.
Baliga M, Uppal N, Ramanathan A. Schwannomas of the head and neck: A case series. J Maxillofac Oral Surg 2009;8 283-6.  Back to cited text no. 21
    
22.
Parikh NR, Desai N. Intraoral schwannoma (neurilemmoma): An unusual anterior palatal swelling - A case report. J Int Oral Health 2010;2:87-91.  Back to cited text no. 22
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]



 

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