Malignant Transformation of Giant Cell Tumor of Bone and the Association with Denosumab Treatment: A Radiology and Pathology Perspective

Figure 3

Case 3, same case as in Figure 2; local recurrence occurred 1 year after curettage, followed by denosumab treatment. After en bloc resection, the diagnosis of malignant GCTB was made. (a) Coronal CT image performed for follow-up approximately 1 year after surgery showed osteolysis along the medial bone-cement interface (arrows) in keeping with local recurrence. Denosumab treatment was started after this scan. (b) Coronal CT image after 10 months of denosumab therapy showed increased density in the osteolytic area of recurrence due to formation of fibro-osseous tissue (vertical arrow at the medial femoral condyle), the tumor expanded further into the soft tissues with an irregular margin (horizontal arrows). In addition, proximal to the area of local recurrence there was a newly formed component of osteoid matrix (dotted arrows), suspicious for progression to osteosarcoma. (c) Photograph of tumor macroscopy (sagittal section) after en bloc resection shows the cementum from the previous surgery, surrounded by tumor tissue extending into the soft tissue. (d) Sagittal CT reformatted after the macroscopy section (Figure 3(c)) shows endomedullary cement and holes due to previous screw tracts, surrounded by denosumab changes (asterisk). Posterior soft tissue mass is noted with osteoid matrix formation suspicious for an osteosarcoma (dotted arrows). (e) Histology at the time of resection; low power view displaying highly cellular spindle cell proliferation with areas of tumor necrosis (left) and the formation of tumor osteoid (right). Scale bar of 50 μm. (f) Tumor osteoid in high-power field fitting with the histological features of an osteosarcoma. Scale bar 50 μm.