TNFSF11 and neoplasm: These findings indicate that this contact-dependent process is RANKL-driven, which means that osteoclast formation and osteolysis occurring in Ewing's sarcoma is through a cell–cell interaction involving RANK-expressing mononuclear phagocyte osteoclast precursors and RANKL-expressing tumour fibroblasts or bone stromal cells in the affected bone.