14-year-old boy suffered from pain in the distal portion of the femur, he then additionally developed progressive swelling (specimen from surgery).
- A section of the distal end of the femur with the epiphysis, epiphyseal plate and diaphysis are shown. The bone in the epiphysis is unremarkable.
- A tumor is seen that diffusely infiltrates the medullary portion of the diaphysis and replaces most of the pre-existing bone trabeculae. The epiphyseal plate is left intact.
- Within the tumor the following components can be distinguished: (1) newly formed already calcified neoplastic bone or osteoid (red) deposited as primitive trabeculae, in broad sheets or exhibiting a lacelike coarse architecture; (2) flanking or captured within the osteoid polymorphic tumor cells, displaying in this case only slightly atypical nuclei.
Direct formation of bone (osteoid) by the tumor cells is crucial for the diagnosis of osteosarcoma. Other matrices including cartilage and fibrous tissue may be formed by the tumor. Portions of the tumors may consist almost exclusively of closely packed spindle cells (anaplastic component). Of note, in the example shown, no high grade features can be distinguished.
Prognosis: Advances in therapy, e.g. pre-operative chemotherapy, have substantially improved prognosis with long-term survival approaching 60-70% compared to earlier rates of 25%.