TNFSF11 and breast cancer: The drug denosumab is an anti-RANKL monoclonal antibody which is used to treat osteoporosis and prevent skeletal damage caused by breast cancer metastases.1 RANK (receptor activator of nuclear factor κB) and its ligand (RANKL) are known for their involvement in bone metabolism.2 Binding of RANKL to RANK on osteoclast precursors induces osteoclast maturation and activation, thereby stimulating bone resorption.