SOX10 lights the path: recognizing rare vulvar schwannoma and review of the literature

Dear Editor,

Benign peripheral nerve sheath tumors are relatively uncommon in the vulvar region, making their recognition important for accurate diagnosis and management. Schwannomas are benign tumors derived from Schwann cells of peripheral nerves. While they are most commonly located in the head, neck, and extremities, involvement of the vulva is exceedingly rare, accounting for less than 1% of benign vulvar neoplasms (1). The differential diagnosis includes neurofibroma, leiomyoma, and other spindle cell lesions, such as cellular angiofibroma and angiomyofibroblastoma (2). The presence of a well-encapsulated mass with Antoni A and Antoni B areas and Verocay bodies is characteristic of schwannoma, although such features may be less prominent in smaller lesions.

We present a case of vulvar schwannoma in a 39 year-old woman, highlighting the critical role of histopathological evaluation and immunohistochemistry (IHC) using Gene - SRY- box transcription factor 10 (SOX10) in establishing an accurate diagnosis. A 39-year-old woman presented with a 1×1 cm, firm, non-tender, mobile swelling over the labia majora for two to three years. There was no history of pain, discharge or neurofibromatosis. The lesion was clinically suspected to be a sebaceous cyst and was excised under local anesthesia. Grossly, the specimen was well-circumscribed with a solid, gray-white to gray-brown cut surface. Histopathological examination revealed an encapsulated tumor composed of spindle cells arranged in fascicles within a collagenous stroma. The nuclei were elongated with tapered ends and pale eosinophilic cytoplasm. No nuclear atypia, mitosis, or necrosis was identified. Numerous thin-walled blood vessels were present. Immunohistochemical staining for SOX10 showed strong nuclear positivity, confirming the diagnosis of schwannoma (Figures 1-3).

SOX10, a nuclear transcription factor, has emerged as a highly sensitive and specific marker for Schwann cell differentiation. It aids in distinguishing schwannoma from other spindle cell tumors that may express S-100 or Desmin focally (3). Immunopositivity for SOX10 thus supports the Schwannian origin, reinforcing its diagnostic utility, particularly in rare anatomical locations like the vulva (4). Table 1 summarizes the current literature (published articles) about vulvar spindle cell tumors and lists key histopathological and immunohistochemical features.

Surgical excision with complete removal of the capsule remains the treatment of choice. The prognosis is excellent, with recurrence being rare if the excision is complete (5). Malignant transformation is exceedingly uncommon. Awareness of this entity and appropriate use of IHC are essential to prevent misdiagnosis as other benign or malignant spindle cell tumors. In conclusion, vulvar schwannoma, although rare, should be included in the differential diagnosis of vulvar spindle cell lesions. SOX10 serves as a valuable adjunct marker for confirmation, ensuring accurate diagnosis and optimal patient management.