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

Figure 1

Case 1, a 54-year-old female with a GCTB in the left ilium. (a) X-ray at presentation shows an osteolytic tumor with cortical destruction (arrowheads) cranially in the left iliac wing, adjacent to the sacroiliac joint. (b) MRI at the time of diagnosis; axial T2 TSE shows an expansive tumor in the left posterior aspect of the ilium with central necrosis and a peripheral thick low signal intensity rim. (c) MRI at the time of diagnosis; T1 SPIR postgadolinium (Gd) shows heterogeneous enhancement, mainly of the tumor rim and adjacent bone marrow edema in the sacrum (arrow) and ilium. (d) Axial unenhanced CT images; 5 months after starting denosumab treatment and (e) 8 months after starting denosumab treatment. Both scans showed no decrease in size and no matrix formation centrally. No thick rim of neocortex was formed. (f) Histology; morphology of first biopsy confirmed the diagnosis of conventional GCTB: mononuclear stromal cells intermixed with osteoclast-like giant cells. The mononuclear cells have slightly enlarged nuclei and predominate over the giant cells, but since overt nuclear atypia and hyperchromasia and atypical mitoses are absent the diagnosis is still compatible with conventional giant cell tumor of bone. In the background reactive lymphocytes and some sclerosis. (g) Immunohistochemistry of the biopsy at the time of presentation: mononuclear stromal cells positive for H3G34W (scale bar 50 μm). (h) Histology of resection after denosumab treatment showed malignant GCTB: atypical cells with enlarged hyperchromatic nuclei, scattered monstrous tumor cells, and atypical mitotic figures with matrix deposition suggestive of tumor osteoid. (i) Immunohistochemistry at the time of resection after denosumab treatment showed atypical stromal cells positive for H3G34W.