Metachronous multicentric giant cell tumor of bone with pulmonary metastases: a case report with 20-year follow-up.

Giant cell tumor of bone (GCTB) is typically a solitary lesion, with multicentric metachronous GCTB (MGCTB) accompanied by pulmonary metastasis being exceedingly rare and posing notable management challenges. A case of MGCTB with 20 years follow up at Union Hospital, Tongji Medical College, Huazhong University of Science and Technology is reported, and relevant literatures are reviewed. This report details a 38-year-old male with MGCTB and pulmonary metastases, followed for over 20 years since his initial treatment in 2005. Despite multiple surgical interventions, including curettage, resection, and eventual amputation, the disease progressed with new osteolytic lesions emerging years later. Systemic therapy with denosumab, initiated in 2017, achieved sustained disease stabilization. Following a treatment interruption during the COVID-19 pandemic, denosumab was resumed in 2021 and effectively controlled systemic lesions; however, a persistently progressing rib lesion necessitated wide en bloc resection in 2022. To date, the patient continues on denosumab with well-controlled disease and no evidence of progression, illustrating its critical role in achieving long-term control in this rare, aggressive GCTB variant. MGCTB is extremely rare. This case underscores the importance of continuous systemic therapy in managing MGCTB, even in the context of surgical interventions.