In this case there is permeative bone destruction of the humerus with involucrum formation and extensive sequestration indicating the disease had been present for some time. The x-ray shows that there is a stalk with continuity of cortex and medullary cavity with the parent bone. Sometimes the stalk will bend away from the joint. Hyaline cartilage overlying lamellar bone. Bone and medullary cavity are in continuity with parent bone.
Diagnosis is osteochondroma.
Yes the femur is a common location for this bone lesion. The appendicular skeleton is the characteristic location with distal femur being the most common location. It probably arises as a developmental defect of the epiphyseal plate. Ages commonly affected are 1-3 decades. 2 cm after skeletal maturity.