Denosumab Therapy for Giant-cell Tumor of the Lumbar Spine: A Case Report and Immunohistochemical Examination

INTRODUCTION: Denosumab, a monoclonal antibody that inhibits the receptor activator of nuclear factor-kappa (RANK) ligand, has been reported to reduce tumor size and progression, promote bone mineralization reconstruction, and increase bone density in patients with giant-cell tumor of bone (GCTB). However, information regarding the histopathological findings of spinal GCTB following denosumab therapy and the time course of the treatment is limited. CASE REPORT: We report the case of a 58-year-old woman with progressive low back pain for 3 months before admission. Radiological and histological examinations revealed L4 GCTB. The patients received 10 courses of denosumab, and the tumor was subsequently resected. The therapy resulted in reduction of tumor mass and replacement of the lesions with bone tissue, particularly at the extravertebral and intracanal mass lesions. Histological examination of resected vertebra revealed a notable decrease in the number of RANK-positive and cyclooxygenase-2-positive cells. However, few RANK-positive cells were present around the woven bone. CONCLUSION: Denosumab therapy for spinal GCTB is effective for reducing the tumor stage, surgical complications, and neurological impairment progression; however, it does not lead to total elimination of GCT cells, and careful consideration is needed in terms of the surgical procedure and post-operative denosumab therapy.