Clinical history: 20 year old male presented with midly painful expansile swelling around the left knee.
Imaging findings:
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- Well defined, expansile lytic lesion noted along the medial aspect of the metadiaphyseal region of the distal left femur (yellow arrow) with mild adjacent periosteal reaction (blue arrows).
- The distal femoral cortex is significantly expanded and thinned out with multiple cortical breaks. No significant associated soft tissue component noted. No matrix calcifications (star).