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| Case nr | Tumor site | X ray/(PET) CT at time of diagnosis | MRI at time of diagnosis | X ray/CT at time of transformation | MRI at time of transformation |
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| 1 | Left ilium | X-ray: lytic lesion with cortex destruction | Thick walled lesion with central necrosis, rim enhancement, and adjacent bone marrow edema | CT after 5 and 8 months of denosumab: absent fibro-osseous matrix and neocortex formation. Unchanged tumor size | Not performed |
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| 2 | L2 | X-ray: lytic lesion with cortex destruction and soft tissue mass | High T2 signal intensity with some foci of low signal | CT: recurrence with right paravertebral soft tissue mass at Th2. No osteolysis of the vertebral body | T2 hyperintense mass in Th2 with large soft tissue component, epidural extension and myelum compression, homogeneous enhancement postcontrast |
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| 3 | Left femur | X-ray: lytic lesion with pathological fracture in the meta-epiphysis. CT showed cortical scalloping and focal cortex destruction | Lesion with high SI on T1 (partly due to hemorrhage after fracture) and T2, heterogeneous. Rim enhancement after contrast | CT of the local recurrence after denosumab showed new cortex destruction with a soft tissue mass, endomedullary irregular sclerosis and new osteoid matrix formation proximally | Not performed |
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| 4 | Left tarsal navicular | X-ray: lytic lesion in the tarsal navicular bone without cortex destruction | Lytic lesion with cortex destruction. Iso-intense on T1, heterogeneous low signal intensity on T2. Extension into lateral cuneiform and cuboid bone | X-ray: resorption of the cancellous bone graft | MRI 3.5 months postcurettage: recurrence around cancellous bone graft, higher signal intensity lesion on T2. Extension into the talocalcaneal joint space.
MRI 7.5 months postcurettage: increase of the recurrence. Extending into tarsalia and calcaneum. High T2 signal (marked increase of signal intensity compared to initial MRI at presentation). Multilobulated appearance. Bone marrow edema+ |
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| 5 | Sacrum | (PET)-CT: osteolysis. SUVmax 21 | Lytic lesion with destruction of cortex, large presacral soft tissue mass. Central cystic/necrotic component high on T2, not enhancing. Low foci on T2 | CT: foci of ossification in the presacral component (on denosumab). Neocortex formation+
No decrease in tumor size | Not performed |
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| 6 | Right femur | X-ray showed a well demarcated lytic lesion in the lateral femoral condyle with a pathological fracture | Not performed | CT: osteolysis adjacent to the cement in the femur and cortex destruction | MRI at the time of first malignant transformation: multifocal recurrence around cement/cancellous bone graft in femur and tibia
MRI 2 yrs later: large heterogeneous soft tissue mass in the popliteal fossa with fast enhancement after contrast |
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