Osteosarcoma of the femur

This is a case of a 15 year old boy who presents with worsening knee pain. The first radiograph demonstrates an ill-defined, mixed lytic and sclerotic mass centered within the medullary cavity of the distal femur. There is thick perisoteal reaction along both the medial and lateral aspects of the distal femoral metadiaphysis. On the lateral radiograph, the thick irregular perisoteal reaction as well as cortical destruction is idenitified. There is a large soft tissue mass extending into both the anterior and posterior compartments of the distal thigh. Based on the patient age, radiographic appearance of the lesion, and location, the most likely diagnosis is osteosarcoma. Osteosarcoma is the most common primary bone maliganncy in the pediatric population. The bones around the knee are the most commonly affected. The other leading differential consideration is Ewings sarcoma. Metastatic disease from osteosarcoma commonly presents in the lung with multiple calcified nodules.