In the bone microenvironment, RANKL is produced by bone marrow stromal cells and osteoblasts, while in a bone tumor environment, it can be produced by other cell types, such as fibroblasts, epithelial cells, or T-lymphocytes, in which RANKL appears to be the final effector of osteoclast-mediated bone resorption (26). The gene discussed is TNFSF11; the disease is bone neoplasm.