Non-ossifying fibroma of the mandibular coronoid process: Report of a rare case

Purpose Non-ossifying fibroma (NOF) is a common benign lesion in pediatric long bones but is exceedingly rare in the craniofacial skeleton, particularly the mandibular coronoid process. This report aims to characterize the clinical, radiological, and histological features of NOF at this atypical location. Case presentation A 26-year-old male presented with a 7-month history of progressive, painless trismus without prior trauma or infection. Panoramic radiography and computed tomography (CT) revealed an expansile, well-corticated, unilocular radiolucent lesion with a foamy internal matrix confined to the left coronoid process, with no soft tissue invasion. Incisional biopsy histology showed a storiform proliferation of spindle-shaped fibroblasts interspersed with scattered multinucleated osteoclast-like giant cells and a complete absence of osteoid formation, establishing the diagnosis of NOF. The patient underwent surgical coronoidectomy via a combined intraoral and extraoral coronal approach. Results and conclusions Postoperatively, mouth opening significantly improved, with no evidence of recurrence at the 3-month follow-up. Although rare, NOF should be considered in the differential diagnosis of osteolytic coronoid lesions. Definitive diagnosis relies on correlating clinical findings with characteristic imaging and histopathology. Complete surgical excision, such as coronoidectomy, appears to be an effective treatment, ensuring good functional recovery and a low recurrence rate.