Recurrent Giant Cell Tumor of Tibia with Pulmonary Metastases: A Case Report

Background: Giant cell tumour of bone (GCTB) is a locally aggressive neoplasm that may recur after treatment and, in uncommon cases, metastasise to the lungs. This report describes pulmonary metastases following recurrent GCTB of the proximal tibia. Case Presentation: A 43-year-old man had previously undergone curettage and bone cement filling for GCTB of the right proximal tibia. Local recurrence developed one year after the initial diagnosis and was treated with subcutaneous denosumab for five months. The patient discontinued treatment without medical advice. Subsequent enlargement of the recurrent mass prompted further imaging and lower-limb amputation. Approximately one year later, he presented with progressive dyspnoea and persistent cough. Chest imaging demonstrated a left mediastinal–pulmonary mass and multiple lesions with a cannonball appearance. Flexible bronchoscopy showed no endobronchial tumour. Histopathological examination of a computed tomography-guided transthoracic needle biopsy identified mononuclear stromal cells and multinucleated giant cells, supporting pulmonary metastasis from GCTB. Clinical and radiological assessment found no recurrence at the amputation site. Following multidisciplinary review, denosumab was selected for further treatment. Conclusion: This case illustrates pulmonary metastatic disease following recurrent proximal tibial GCTB despite extensive local treatment. It supports consideration of continued clinical surveillance and individualised assessment of pulmonary lesions. The temporal association between treatment discontinuation and disease progression does not establish causality.