Cytokeratin-Positive Osteosarcoma Simulating Sarcomatoid Metastatic Carcinoma

Figure 4

(a) Post-EBRT X-ray of the involved distal femur shows some periosteal reaction developing. Intramedullary sclerotic changes are seen reflecting the introduction of bone cement after the initial biopsy. (b) Postradiotherapy MRI demonstrating the lesion has increased in size since the previous examination now measuring 8.5 cm in the cephalocaudal dimension and 4.5 cm in the transverse dimension with evidence for postoperative change within the lesion. Patchy areas of increased signal within the medullary space of the mid to distal femur as well as the proximal tibia and patella most likely are related to postradiation change. The focal prominent region of decreased signal within the lesion corresponds to interval biopsy, curettage, and cementation. (c) Dark heterogeneous signal on T1W and brighter signal intensity on T2W sequences.

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