Desmoplastic fibroma of the mandible in a child: a case report with more than 3 years of radiographic follow-up Manuscript prepared for submission to BMC Oral Health

Abstract Background: Desmoplastic fibroma (DF) is a rare, benign but locally aggressive intraosseous fibroblastic neoplasm. Jaw involvement is uncommon, and diagnosis may be challenging because its clinical and radiographic appearance overlaps with other odontogenic and fibro-osseous lesions. Case presentation: We report a pediatric case of left mandibular DF in a 6-year-old boy. Imaging demonstrated an osteolytic destructive lesion involving the left mandibular body, with cortical destruction and close relationship to the inferior alveolar canal and developing permanent teeth. Histopathologic examination of an incisional biopsy showed a hypocellular spindle-cell neoplasm arranged in fascicles within abundant collagen, with mild pleomorphism, no necrosis, and fewer than 1 mitosis/10 high-power fields. Immunohistochemistry showed tumor-cell positivity for smooth muscle actin, focal desmin and β-catenin, negative H-caldesmon and S100, and a low proliferative index of approximately 1–2% by Ki-67. The overall clinicoradiologic and pathologic findings favored DF. The lesion was surgically treated and followed by serial radiographic surveillance. Follow-up imaging documented progressive mandibular remodeling without definite evidence of recurrence through approximately 3 years after treatment. Conclusion: This case highlights the importance of clinicoradiologic-pathologic correlation in pediatric mandibular DF and the value of prolonged surveillance after surgery. 1-cm surgical margin was documented in the operative report. Published mandibular DF cases have similarly used 1-cm safety/free margins in selected resections, supporting the adequacy of this margin in the present case.