Fibrous Dysplasia Developed at the Site of a Previous Central Giant Cell Granuloma in a Middle-Aged Patient: A Case Report.

Background and Aim: Fibrous dysplasia (FD) is a benign fibro-osseous condition, characterized by replacement of normal bone with immature fibrous tissue due to GNAS mutations, whereas central giant cell granuloma (CGCG) is a reactive lesion featuring multinucleated giant cells in a vascular stroma. Although some hybrid lesions combining FD and CGCG have been reported as synchronous entities, metachronous occurrences, where FD develops years after CGCG excision, are rare. This report describes a case of metachronous FD arising at the site of a previously excised CGCG after a 10-year interval, exploring potential temporal association and emphasizing the need for extended follow-up. Case Presentation: A 50-year-old woman presented with a firm, gradually enlarging swelling in the right maxilla that had developed over 2 years. Her history included surgical excision of a pure CGCG (no fibro-osseous elements) in the same location 10 years prior. Clinical examination revealed bony-hard expansion without neurosensory deficits or lymphadenopathy. Cone-beam computed tomography showed a poorly defined, expansile radiopaque mass with a ground-glass pattern, obliterating the maxillary sinus. An incisional biopsy showed evidence of FD, with irregular woven bone trabeculae in fibrous stroma lacking osteoblastic rimming. Conclusion: To the best of our knowledge, this is one of the first reported metachronous cases of FD arising de novo at the site of a previously excised CGCG following a 10-year interval. This report underscores the importance of long-term follow-up for patients with jaw pathologies to detect rare sequential developments.