NCIt definition : A high grade malignant bone-forming mesenchymal neoplasm that produces osteoid and
occurs in childhood. It arises from the medullary portion of the bone. It affects
the long bones, and most commonly, the distal femur, proximal tibia, and proximal
humerus. Pain with or without a palpable mass is the most common clinical presentation.
It usually has an aggressive growth and may metastasize through the hematogenous route.
The lung is the most frequent site of metastasis.;
Alternative definition : NICHD: A conventional osteosarcoma occurring during childhood.;