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Case Reports in Medicine
Volume 2015, Article ID 767198, 6 pages
Case Report

Two Cases of Sarcoma Arising in Giant Cell Tumor of Bone Treated with Denosumab

1Department of Pathology, University of New Mexico School of Medicine, MSC08 4640, 1 University of New Mexico, Albuquerque, NM 87131, USA
2Department of Orthopaedics, University of New Mexico School of Medicine, MSC10 5600, Albuquerque, NM 87131, USA
3Department of Radiology, University of New Mexico School of Medicine, MSC10 5530, 1 University of New Mexico, Albuquerque, NM 87131, USA

Received 29 August 2015; Revised 2 December 2015; Accepted 3 December 2015

Academic Editor: Gottfried J. Locker

Copyright © 2015 Cory Julian Broehm et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Giant cell tumor (GCT) of bone is a generally benign, but often locally aggressive, neoplasm of bone, with a propensity for recurrence. Sarcomatous transformation is rare and typically occurs with a history of recurrences and radiation treatment. Denosumab, an inhibitor of the RANK ligand involved in bone resorption in GCT, is increasingly used in treatment of recurrent or unresectable giant cell tumor of bone. We report two cases of sarcomatous transformation of GCT to osteosarcoma in patients receiving denosumab. One was a 59-year-old male with a 12-year history of GCT and multiple recurrences taking denosumab for 2.5 years. The second case was in a 56-year-old male with a seven-year history of GCT taking denosumab for six months. Review of the literature shows one case report of malignant transformation of GCT in a patient being treated with denosumab. As the use of denosumab for treatment of GCT will likely increase, larger, controlled studies are needed to ascertain whether denosumab may play a role in malignant transformation of giant cell tumor of bone.