Uterine leiomyosarcoma with osteoclast-like giant cells associated with high expression of receptor activator of nuclear factor κB ligand.

The occurrence of osteoclast-like giant cells (OLGCs) in uterine leiomyosarcomas (LMSs) is a rare phenomenon. The nature of OLGCs and the significance of their accumulation in these tumors are poorly understood. Recent studies revealed that the formation of osteoclasts requires a specific cytokine, receptor activator of nuclear factor κB ligand (RANKL), in bone. In this study, we investigated the expression of RANKL in 2 cases of uterine LMS with OLGCs by means of immunohistochemistry and compared the extent of RANKL expression with that in conventional uterine LMSs and leiomyomas by using real-time reverse-transcription quantitative polymerase chain reaction. Our cases of uterine LMS with OLGCs showed markedly high expression of RANKL messenger RNA with clear RANKL immunoreactivity compared with messenger RNA expression and immunoreactivity of conventional uterine LMSs and leiomyomas. These findings suggest that the tumors producing RANKL may account for accumulation of OLGCs in tumor tissue because of RANKL-related osteoclastogenesis.