NCIt definition : A low grade malignant bone-forming mesenchymal neoplasm arising from the surface of
the bone. It occurs in childhood and usually affects the distal posterior femur, the
proximal tibia, and proximal humerus. Painless swelling is the usual clinical sign.
The prognosis is usually excellent.;
Alternative definition : NICHD: A parosteal osteosarcoma occurring during childhood.;