A Rare Case of Buccal Mucosa Schwannoma with Atypical Presentation

Abstract

Schwannomas are benign peripheral nerve sheath tumors, rarely found in the oral cavity. The buccal mucosa is an especially uncommon site, posing diagnostic challenges due to their resemblance to other soft-tissue lesions. We present the case of a 33-year-old male with a slow-growing, purplish-black lesion in the right buccal mucosa. Clinical, radiological, and histopathological evaluations confirmed the diagnosis of schwannoma. Schwannoma, though rare in the buccal mucosa, should be included in the differential diagnosis of intraoral swellings. Histopathology remains essential for definitive diagnosis and treatment planning.

INTRODUCTION

Schwannomas, also known as neurilemmomas, are benign, encapsulated neoplasms that arise from Schwann cells, which form the myelin sheath surrounding peripheral nerves. These tumors can occur anywhere in the body except in the optic and olfactory nerves, which lack Schwann cells due to their central nervous system origin.[1] Head-and-neck schwannomas constitute approximately 25%–45% of all schwannomas.[2] However, intraoral schwannomas are rare, comprising only 1% of these tumors, with the tongue being the most frequently affected site.[3]

Involvement of the buccal mucosa is particularly uncommon, making diagnosis challenging due to its resemblance to more frequently encountered intraoral lesions such as mucoceles, lipomas, fibrous histiocytomas, or vascular anomalies.[4] Schwannomas typically present as slow-growing, asymptomatic masses that may persist for years before being detected.[5] However, they can occasionally present with discomfort, paresthesia, or interference with oral function depending on their size and anatomical location.[6]

Histopathologically, schwannomas are characterized by biphasic tissue patterns – Antoni A and Antoni B areas – demonstrating palisading of spindle-shaped cells and myxoid regions, respectively.[7] Verocay bodies, formed by acellular eosinophilic areas bordered by palisading nuclei, are hallmark features of Antoni A tissue.[8] Some tumors exhibit degenerative features such as hemorrhage, cystic changes, or cellular atypia – features characteristic of the “ancient schwannoma” variant.[9]

Given their indolent course and resemblance to other benign soft-tissue lesions, early clinical suspicion followed by histopathologic confirmation is essential for accurate diagnosis and management. This report presents a rare case of schwannoma arising in the buccal mucosa with an unusual purplish-black appearance, underscoring the importance of including schwannoma in the differential diagnosis of atypical intraoral swellings.

CASE REPORT

A 33-year-old male presented with a 3–4-month history of a slow-growing swelling in the lower right buccal mucosa. The swelling was purplish-black in appearance and gradually increased in size, leading to discomfort while chewing. There was no associated pain, bleeding, or trauma. Medical, dental, and family histories were noncontributory.

Extraoral examination revealed no facial asymmetry, temporomandibular joint dysfunction, or cervical lymphadenopathy.

Intraoral examination revealed a soft-to-firm, ovoid, purplish-black lesion measuring approximately 3 cm × 3 cm in the right buccal mucosa, extending from the distal aspect of tooth 46 to the retromolar pad anteroposteriorly and from 1 cm above the occlusal plane to the alveolar ridge in the region of teeth 47 and 48. The lesion was mobile, nontender, well-defined and showed no signs of ulceration or discharge [Figure 1]. Diascopy and slip sign tests were negative, indicating a nonvascular lesion. No cervical lymphadenopathy or neurological deficits were observed.

Figure 1.

Preoperative intraoral view of that lesion

Diagnostic assessment

Based on the clinical presentation, a provisional diagnosis of a benign soft-tissue tumor of neural origin was made. Differential diagnoses included lipoma, fibrous histiocytoma, and leiomyoma.

Investigations performed included a complete hemogram (normal) and orthopantomogram, which showed no bony involvement. An excisional biopsy was carried out under local anesthesia [Figure 2]. The excised lesion was sent for histopathological analysis [Figure 3].

Figure 2.

Intraoperative procedure removal of lesion

Figure 3.

Excised lesion

Histopathological findings

Microscopic examination revealed a partially encapsulated lesion with a fibrous capsule composed of thick collagen bundles. Beneath the capsule, spindle-shaped Schwann cells with wavy, dark-stained nuclei were arranged in palisading patterns, forming Antoni A areas. Acellular eosinophilic Verocay bodies were observed between the palisading cells. Antoni B areas exhibited loosely arranged spindle cells in a myxoid stroma. Large blood vessels with hyalinized walls, microcystic spaces, and mild chronic inflammatory infiltrate consisting of lymphocytes and plasma cells were also present. Rare mitotic figures and mild cellular atypia were noted. These features confirmed the diagnosis of schwannoma (neurilemmoma) [Figure 4].

Figure 4.

Low-power photomicrograph of Schwannoma of the buccal mucosa (H and E stain, ×40)

Follow-up and outcome

Postoperative recovery was uneventful. The patient was prescribed antibiotics and analgesics. A follow-up at 15 days showed complete healing of the surgical site. The overlying mucosa appeared healthy, and the patient reported resolution of chewing discomfort. No recurrence, neurological deficits, or complications were observed over the next 3 months. The patient continues to be monitored on a biannual basis, with no signs of recurrence to date.

DISCUSSION

Schwannomas are benign peripheral nerve sheath tumors with a well-encapsulated histologic structure, typically composed of Antoni A and Antoni B areas.[1,2] Although they most commonly occur in the tongue, their presence in the buccal mucosa is rare.[3] Due to their slow growth and asymptomatic nature, they often go undiagnosed until significant growth or interference with oral function occurs.

The purplish-black coloration of the lesion in this case was atypical for schwannomas and raised initial suspicion for a vascular lesion.[4] However, histological analysis revealed spindle-shaped Schwann cells in Antoni A areas, Verocay bodies, and less cellular Antoni B areas, confirming the diagnosis.[5] Ancient schwannomas exhibit degenerative changes, including hemorrhage, cystic degeneration, and cellular pleomorphism, but remain benign.[6]

Immunohistochemistry can aid in differentiating schwannoma from other spindle cell tumors. Schwannomas typically show strong S-100 positivity.[7] Complete excision is curative with a low recurrence rate.[8]

Strengths and limitations

This case demonstrates a thorough diagnostic approach combining clinical examination, imaging, and histopathology. A limitation was the inability to perform advanced imaging (e.g., magnetic resonance imaging), which could have provided better delineation of the lesion’s extent and nerve involvement.

Medical literature context

Intraoral schwannomas most frequently affect the tongue and are usually asymptomatic. Buccal mucosa involvement is extremely rare. Few published reports document similar cases, and even fewer present with a purplish-black hue, a feature that initially suggested a vascular lesion or hemorrhagic component. This unusual coloration may result from hemorrhagic degeneration or chronic inflammatory changes.

Diagnostic challenges

The clinical presentation was misleading due to the lesion’s color and mobility, initially raising suspicion for vascular malformation or lipoma. Only histological evaluation revealed the classic features of schwannoma.

Rationale

Complete surgical excision was both diagnostic and therapeutic. Histopathology confirmed the diagnosis and ruled out other possibilities such as lipoma (which lacks Antoni A/B areas), fibrous histiocytoma (which shows fibroblastic and histiocytic cells), and leiomyoma (which shows interlacing fascicles of smooth muscle).

CONCLUSION

This case highlights the importance of considering schwannoma in the differential diagnosis of intraoral swellings, especially when clinical presentation is atypical. Histopathological evaluation remains essential for definitive diagnosis. Surgical excision results in favorable outcomes, as demonstrated in this case.

Ethical approval and consent to participate

Written informed consent was obtained from the patient for participation and publication.

Declaration of patient consent

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

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.