TNF and Ewing sarcoma: Although TNFα can directly induce OC formation from TAMs in Ewing’s sarcoma in the presence of M-CSF [172], it is unknown if TNFα- induced OCs from TAMs have any difference with those from normal macrophages, because TNFα induces RANKL-independent OC formation from normal macrophages [72,86,87,88,91,93].