Sinonasal osteosarcoma of the ethmoid bone with decade-later recurrence presenting as early orbital apex syndrome: an 18-year case report.

Introduction: Primary ethmoid osteosarcoma is an exceptionally rare craniofacial malignancy, characterized by aggressive local invasion of adjacent structures. While most recurrences occur within the first 2-3 years, late relapse after long-term disease-free survival is exceedingly uncommon. Case presentation: We describe an 18-year clinical course of a patient first diagnosed with ethmoidal chondroblastic osteosarcoma in childhood. He was treated with chemotherapy and radiation therapy and went into remission. Seven years later, the cancer recurred in the sinuses and lungs. He underwent surgery and more chemotherapy, then remained stable for nearly a decade. After that, he developed worsening nasal blockage, nosebleeds, eye bulging, and sudden vision loss consistent with orbital apex syndrome. Scans showed a destructive mass eroding the skull base and reaching the orbital apex. He underwent endoscopic surgery to remove the tumor, decompress the optic canal, and reconstruct the skull base. Pathology confirmed another recurrence. After surgery, his vision improved to light perception, and he started a new round of chemotherapy. Clinical discussion: This case shows that sinonasal osteosarcoma can recur very late, so lifelong monitoring with CT and MRI is necessary. Sudden ocular symptoms in these patients should be treated as emergencies to preserve vision. An endoscopic approach allowed safe access to the skull base and effective orbital decompression. Conclusion: Timely multidisciplinary care and continued follow-up are essential for rare malignancies, even after many years without disease.