Abstract
Giant cell tumour of bone is a benign, locally aggressive osteolytic tumour that typically affects skeletally mature young individuals. It predominantly emerges within the metaphysis, extending towards the epiphysis of long bones, while occurrences in flat bones are exceptionally rare. We present a case of a woman in her late 20s who presented with a large right ischial mass. A biopsy confirmed the mass as a giant cell tumour. The tumour extended to the acetabulum, and due to the potential risk of significant bleeding and contamination during en bloc excision, a prudent approach involved initiating denosumab therapy, a monoclonal antibody targeting receptor activator of nuclear factor-κB ligand therapy, before proceeding with radical surgery. Denosumab therapy successfully rendered a previously inoperable tumour favourable for surgical intervention. We went on to perform a type 2 and 3 internal hemipelvectomy, followed by a reconstruction with a hip endoprosthesis replacement.