Endoscopic Resection of A Sinonasal Ossifying Fibroma in a Patient With Sigmoid Sinus Thrombosis: A Case Report

We report a rare case of a 30-year-old male patient with known factor V Leiden mutation, presented to an outside hospital with severe right-sided headache and nasal obstruction of two weeks. He had been diagnosed with sphenoid sinusitis and thrombosis of the left sigmoid sinus/proximal internal jugular vein and treated with antibiotics and anti-coagulants in a different hospital with minimal improvement. Nasal endoscopy at our instituition revealed purulence in the right sphenoethmoidal recess, with no masses seen in the nasal or oral cavity, and with normal extraocular muscle function. A CT scan demonstrated a well circumscribed lobulated lesion measuring 4.0 × 2.6 × 2.3 cm (AP × CC × TR) in the right sphenoid and posterior ethmoid sinuses, without bone erosion or orbital extension. The mass was heterogeneous with small fibrous hypodense areas and large hyperdense areas of mineralization. The tumor was completely excised via expanded endonasal approach by our skull base surgery team. Histopathology confirmed ossifying fibroma, a benign tumor with potentially locally aggressive evolution and a high risk for recurrence, that rarely affects the sinonasal tract. The postoperative course was uneventful, and early follow-up showed no recurrence after complete resection and total resolution of his symptoms. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany