case of of Primary Malig...

A 12 year old presented to the emergency department with a chief complaint of bilateral knee joint pain and lower leg pain. He also reported multiple swellings over both knee joints and in the leg region,difficulty in walking, stiffness in the bilateral knee joint since he was one year. No Medical History seen. On physical examination, the swelling was in the region of the metaphysic of the distal end of the bilateral femur and proximal end of the bilateral tibia, skin over the swelling was shiny with tenderness and irregularity.Kindly Suggest appropriate diagnosis and treatment for this case.