Tumor Transformation: Case of conversion of Ossifying Fibroma to Osteosarcoma post-excision in a young male

Ossifying fibroma (OF) is a benign fibro-osseous tumor characterized by slow growth and a low recurrence risk, primarily affecting the mandible in young females. Although OF is typically non-invasive, rare cases demonstrate locally aggressive behavior, requiring surgical resection. Post-surgical transformation of into osteosarcoma, a rare malignancy with a prevalence of 0.7 per million in the jaw, is exceptionally uncommon. This report presents a rare case of a 28-year-old male initially diagnosed with ossifying fibroma, managed surgically through excision and reconstruction with an iliac crest graft. Despite achieving negative margins, the lesion underwent malignant transformation into fibroblastic osteosarcoma within a month, presenting diagnostic and therapeutic challenges.

The malignant transformation was confirmed through histopathological and immunohistochemical evaluations, revealing a high Ki-67 labeling index (60 %), indicative of aggressive tumor behavior. Following multidisciplinary tumor board discussions, the patient underwent extensive surgical management, including composite resection, segmental mandibulectomy, neck dissection, and microvascular reconstruction with a free fibula osteocutaneous flap. Despite its rarity, this case highlights the need for vigilant follow-up and comprehensive diagnostic workups for recurrent or progressive lesions post-OF resection.

This report contributes to the limited literature on malignant transformation in fibro-osseous lesions, emphasizing the importance of differentiating benign conditions from low-grade malignancies and discussing the role of surgical intervention in such transformations. Further research is required to elucidate the mechanisms of transformation, optimize management strategies, and improve outcomes for patients with similar rare pathologies.