Unusual evolution of a benign-looking cortical defect of the proximal humerus. A case of intracortical osteosarcoma?

A case of an osteosarcoma following a pathological fracture through a small benign-looking cortical lesion of the proximal humerus is described. The unusual evolution from a small cortical lesion to a malignant lesion raises the question whether this is a case of an intracortical osteosarcoma that has some distinct features from those of previously reported cases.