Pseudomyogenic hemangioendothelioma of bone treated with denosumab: A case report

Background: Pseudomyogenic hemangioendothelioma (PMHE) is a rare endothelial neoplasm that involves the bones in only 14% of all cases. The optimal treatment strategy has not been established. We herein report a case of primary PMHE in which denosumab treatment showed activity in both imaging studies and the clinical outcome. Case presentation: A 20-year-old woman presented with worsening pain in her left ankle. Imaging studies showed multifocal fluorodeoxyglucose (FDG)-avid [maximum standardized uptake value (SUVmax), 15.95] osteolytic lesions in the bones of her left lower extremity. While waiting for the definitive pathologic diagnosis of PMHE, denosumab, a human immunoglobulin G2 monoclonal antibody against RANKL, was initiated to treat progressive bone absorption after curettage of one of the lesions. Denosumab induced osteosclerosis around the lesions and pain relief and was discontinued 4 years after its initiation. Although all of the multifocal lesions remained, they all became less FDG-avid (SUVmax, 2.6), and the patient developed no signs of new lesions or distant metastasis. Conclusion: Denosumab plays a certain role in prevention of bone destruction by PMHE through suppression of osteoclast-like giant cells and would be an excellent treatment for bone absorption by PMHE of bone.