[Giant cell tumour of bone in the rib cage treated with denosumab. A case report]

Giant cell tumour of bone (GCTOB) accounts for 4-5% of all primary bone tumours and occurs most frequently in females between 20 and 45 years old. It is found in the epiphyses of the long bones, vertebral bodies and flat bones. We report the case of a 31-year-old woman who presented with a one month history of thoracic pain. On examination, a mass was found in the right breast with signs of an ipsilateral pleural effusion. A thoracic CAT scan revealed an infiltrating mass which was subsequently biopsied and a GCTOB was diagnosed. Due to the localization and the morphology, a wide range of differential diagnoses were considered. Genetic studies detected a mutation of the gene H3F3A, supporting the original diagnosis. The patient underwent treatment with denosumab followed by surgical resection of the mass. The histopathology of the tumour revealed various histological changes which were a source of diagnostic pitfalls.