Malignant Schwannoma of the Infratemporal Fossa with Perineural Extension in a Young Female: A Case Report

Background : Malignant peripheral nerve sheath tumors (MPNSTs), historically referred to as malignant schwannomas, are rare soft tissue sarcomas originating from Schwann cells or peripheral nerve sheath elements. Head and neck involvement accounts for only a small proportion of cases, while localization within the infratemporal fossa is exceptionally uncommon. The deep anatomical location, proximity to critical neurovascular structures, and nonspecific clinical presentation often delay diagnosis.Case Presentation : We report the case of a 20-year-old woman with no significant past medical history who presented with a nine-month history of progressive left cheek swelling. Clinical examination revealed a firm, fixed, painless jugal mass measuring approximately 5 cm without inflammatory signs. Cranial nerve examination demonstrated preserved trigeminal nerve (V1 and V2) sensation. Nasal endoscopy was unremarkable. Magnetic resonance imaging demonstrated a 32.4 × 42.7 × 50 mm parapharyngeal and infratemporal fossa mass exhibiting multidirectional extension along neural pathways toward the pterygopalatine ganglion. Complete surgical excision was achieved through a Le Fort I osteotomy approach. Histopathological and immunohistochemical analyses showed focal nuclear positivity for S100 protein and negativity for cytokeratin, smooth muscle actin, CD34, HMB45, and desmin, supporting the diagnosis of malignant schwannoma (FNCLCC grade II). Surgical margins were negative. The patient subsequently underwent adjuvant radiotherapyConclusion : MPNSTs of the infratemporal fossa remain exceedingly rare. Complete surgical resection with tumor-free margins remains the cornerstone of treatment, while adjuvant radiotherapy may improve local disease control. Early recognition and multidisciplinary management are essential to optimize outcomes.