TNFSF11 and plasma cell myeloma: Dysregulation of the RANKL/RANK/OPG system has been detected in several tumors, such as breast cancer[12], [13], prostate cancer[14], malignant bone tumors (e.g., multiple myeloma, giant cell tumors of bone, and chondroblastoma)[15]–[17], squamous cell carcinoma[18], and Hodgkin disease[19].