My child has a hard mass over the thigh

Case PresentationA 10-year-old boy was brought to the clinic by his parents, complaining of a palpable, slow growing hard mass over the distal left thigh for the past one year.There were no other swellings present on other parts of the body.His parents were worried since the swelling had increased in size over time.However, the child did not complain of any pain or any local pressure symptoms.He did not recall any obvious trauma to the limb.He did not have any constitutional symptoms.He was an active child and did not have any problems at school.Clinically, there was a hard round mass over the distal anterior left thigh with a well-defined border, measuring 8 x 8 cm.It was non-mobile and fixed to the underlying bone.The overlying skin was normal with no signs of inflammation.Range of movement of the knee was normal.Plain radiograph of the left femur was done (Figure 1 a,b).