Giant Olfactory Cleft Schwannoma Arising from the Nasal Septum: A Case Report with Immunohistochemical Insights

Background Olfactory cleft schwannomas arising from the nasal septum are exceedingly rare, with fewer than 50 cases documented globally. Preoperative differentiation from other sinonasal spindle cell tumors remains challenging due to overlapping clinical and imaging features. Methods Here, we report a case of A 43-year-old woman presented with a 2-month history of progressive left nasal obstruction and intermittent epistaxis. Nasal endoscopy revealed a 3.5 × 2.8 cm smooth-surfaced mass originating from the posterior nasal septum within the left olfactory cleft. Computed tomography (CT) demonstrated a nodular lesion with local septal cartilage compression. Endoscopic cryo-plasma resection under general anesthesia achieved complete tumor removal while preserving septal integrity. Histopathology confirmed a benign schwannoma characterized by spindle cells arranged in Antoni A/B patterns, strong diffuse S-100 (++++) and CD34 (++++) positivity, and low proliferative activity (Ki67: 3%). Margins were tumor-free on intraoperative frozen section. No recurrence was observed at 6-month follow-up. Conclusion This case underscores the diagnostic utility of immunohistochemistry (S-100, CD34) in distinguishing schwannomas from neurofibromas, hemangiomas, and other sinonasal tumors. Endoscopic cryo-plasma excision offers a minimally invasive approach for septal schwannomas, ensuring complete resection with reduced morbidity. Long-term surveillance remains essential given the rarity of recurrence.