Acute lymphoblastic leukemia


This is pathologically proven acute lymphoblastic leukemia (ALL).

The initial diagnosis is confounded by the fairly atypical, patchy and well defined bone lesions - rather than diffuse marrow infiltration - in a clinically well child, presenting with a single region complaint (knee pain) in an outpatient setting.  Extensive metastases is a differential.  

Concurrent anterior tibial marrow edema with suspected microtrabecular fracture and overlying pretibial edema, most likely due to acute injury, leading to presentation and ultimately her diagnosis.