Final diagnosis:

Right humerus, biopsy: low grade cartilaginous neoplasm.

Sections show hypocellular disorganized cartilage with some myxoid change, mild chondrocyte atypia and focal chondrocyte necrosis. Permeative growth is not seen. By histology alone, this lesion could represent either a cortical chondroma or low grade juxtacortical chondrosarcoma (clinical correlation is required). There are no high grade areas in this biopsy specimen.