Extracranial hypoglossal nerve schwannoma presenting as a submandibular gland tumor: diagnostic pitfalls and surgical considerations—a case report

Schwannomas are benign, encapsulated tumors arising from Schwann cells. Extracranial hypoglossal nerve schwannomas located in the submandibular region are exceptionally rare and may clinically and radiologically mimic primary submandibular gland tumors. A 44-year-old woman presented with a painless left submandibular mass of three months' duration. Ultrasonography and contrast-enhanced computed tomography demonstrated a well-circumscribed heterogeneous lesion closely associated with the left submandibular gland, and a pleomorphic adenoma was suspected preoperatively. Preoperative needle biopsy was not performed because of concern regarding sampling error and a potentially nondiagnostic result. Magnetic resonance imaging was not performed because of financial considerations and the patient's reluctance to undergo further examination. During surgery, the encapsulated tumor was found to arise from the hypoglossal nerve and was carefully dissected from the nerve sheath while preserving the anatomical continuity of the main nerve trunk. Histopathological and immunohistochemical examinations confirmed schwannoma. At the one-year follow-up, the patient showed normal tongue movement without recurrence or neurological deficit. A review of published reports indicates that extracranial hypoglossal nerve schwannomas have been reported to present as painless submandibular masses and may be misdiagnosed before surgery. This case emphasizes that preoperative recognition of hypoglossal nerve origin may facilitate appropriate surgical planning and may allow preservation of both the functional nerve and the uninvolved submandibular gland.