Are these appearances aggressive?
This lesion demonstrates a mixture of features. The sharply defined slightly sclerotic margins and absence of periosteal reaction favour a non-aggressive lesion, however transgression of the growth plate suggests a more aggressive process. Cortical breach in this case appears to be a pathological fracture rather than cortical destruction.
Given the sharply defined slightly sclerotic margins, absence of periosteal reaction and location in the epiphysis prior to growth plate closure, which entity do you favour?
Chondroblastoma (this was confirmed histologically).
CT confirms the plain film appearances, revealing a sharply demarcated epiphyseal lucent lesion but with faintly sclerotic margins. It transgresses the growth plate into the anterior part of the metaphysis. There is no periosteal reaction, however the does appear to be a cortical breach anterosuperiorly into the knee joint. No matrix calcification or extra-osseous soft tissue component can be demonstrated.