|Year : 2015 | Volume
| Issue : 3 | Page : 484-487
Rare case of palatal schwannoma: Case report and review of literature
Uday Shankar Yaga, Ashwini Kumar Mengji, Radhika Besta, Nishanth Gollamudi
Department of Oral Medicine and Radiology, MNR Dental College and Hospital, Sangareddy, Telangana, India
|Date of Submission||04-Mar-2015|
|Date of Acceptance||03-Nov-2015|
|Date of Web Publication||25-Nov-2015|
Department of Oral Medicine and Radiology, MNR Dental College and Hospital, Sangareddy - 502 294, Telangana
Source of Support: None, Conflict of Interest: None
| 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. , 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|| |
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.  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.  Although these benign tumors may affect any site of the body, in the head and neck region, the incidence is around 25-48%.  Intraoral occurrence of schwannomas is rare with an incidence of about only 1%.  The sites of occurrence are usually the tongue, palate, floor of mouth, buccal mucosa, and mandible in descending order of incidence.  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. , 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.  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|| |
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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| Discussion|| |
Schwannoma, also known as neurilemmoma or neurinoma or perineural fibroblastoma,  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.  Verocay first described them as neurinoma in 1908. , 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). 
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). 
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.  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.  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.  In a review done by Leu and Chang,  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.  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.
Radiographically, intraosseous schwannomas appear as unilocular radiolucencies with very thin sclerotic border. Sometimes the neighboring teeth may show external root resorption and cortical expansion. , 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. 
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.  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  and glial fibrillary acidic protein (GFAP) in many cases.  The pericapsular region of a schwannoma may contain CD34-positive cells. 
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. , As recurrence and malignant transformation of neurilemmoma are exceedingly rare, the prognosis is usually very good.  In the present case, the mass was well encapsulated and could be totally excised. The prognosis was good.
| Conclusion|| |
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.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]