Chondromyxoid Fibroma of the Proximal Fibula, a Rare Benign Bone Tumor With Unusual Location: A Case Report.

Case: An 11-year-old female presented with a painful mass in the right proximal leg. Radiographs revealed a geographic osteolytic lesion involving the metaphysis and extending into the diaphysis of the proximal fibula. She underwent extended curettage with adjuvant electrocautery and 95% ethanol for tumor ablation. The resulting defect was reconstructed using morselized talus allograft. At 18 months postoperatively, there was no evidence of local recurrence, bone remodeling was complete, and the patient achieved full functional recovery with an MSTS score of 100%, resuming unrestricted physical activity. Conclusion: This case highlights the diagnostic and therapeutic complexities associated with chondromyxoid fibroma (CMF) in atypical anatomical sites such as the proximal fibula. The use of extended curettage combined with adjuvant modalities and allograft reconstruction demonstrated favorable oncologic and functional outcomes. These findings contribute to the evolving evidence base for managing CMF in rare locations, underscoring the need for further studies to optimize treatment strategies.