Although osteosarcomas are the most frequent primary bone tumours, they account for less than 1% of all cancers diagnosed in the United States.1 Low-grade central osteosarcoma (LGCOS) accounts for only 1.2% of all osteosarcomas.2 The aetiology of LGCOS is not fully elucidated, except for Ragazzini et al. reporting that SAS, MDM2 and CDK4 genes may be involved in tumourogenesis and progression of this tumour.3 This very rare bone tumour has a good prognosis when the excision with wide margins can be achieved. The gene discussed is CDK4; the disease is bone neoplasm.