Beta-Catenin Positive Giant Cell Tumor of Bone with Pathological Fracture Treated with Neoadjuvant Denosumab Therapy for Visualizing Extraskeletal Lesions.

Introduction: Giant cell tumors of bone (GCTBs) are locally aggressive tumors that can induce pathological fractures. Previous reports suggest that denosumab induces intratumoral ossification in β-catenin positive GCTB. However, its effect on the complete resection of GCTB with extraskeletal lesions remains unclear.

Case presentation: A 45-year-old woman with a pathological fracture of the left distal femur was diagnosed with GCTB based on the biopsy findings, which revealed both H3.3 G34W and nuclear β-catenin positivity. Eight courses of neoadjuvant denosumab therapy were administered to visualize the extraskeletal lesions; subsequently, en bloc resection with megaprosthetic reconstruction was successfully performed. Pathological examination revealed intratumoral ossification without osteoclastic giant cells. Two years after the surgery, no evidence of local recurrence was recorded.

Conclusion: Neoadjuvant denosumab therapy is an effective approach for managing β-catenin positive GCTB with pathological fractures as it promotes intratumoral ossification and facilitates complete resection of GCTB, including extraskeletal lesions.