Giant cell tumour (GCT) of the anterior arc of a rib is a very rare occurrence and quite often the diagnosis is delayed. We report a case of GCT of a rib arising from the anterior arc which presented as a breast lump. The diagnosis of GCT was considered in the differentials only when percutaneous biopsy revealed multinucleated osteocleastic giant cells. Further diagnosis was confirmed by spotted oblique radiographs and computed tomography (CT). Surgical excision with repair of the chest wall by a mesh was done. The postoperative histopathological examination of the resected specimen confirmed the preoperative diagnosis of giant cell tumour. The present article aims to aware the reader about such rare presentations of GCT, which should be included in the differential diagnosis of a tumour originating from the anterior arc of the rib.