Ostoesarcomas most commonly occur in the metaphyses (flared regions) of the long bones.
The long bones gain their length by extending at the epiphyses (growth plates) at each end of the bone, leaving new bone behind which becomes the metaphysis and diaphysis (shaft).
The distribution of osteosarcomas closely follows the amount of growth each epiphysis has to contribute. Thus the longest bone, the femur is the most common bone involved. The femur gains most of its length distally, and most femoral osteosarcomas are located distally.
In children and adolescents:
- More than 50% of these tumors arise from the bones around the knee
- Approximately one-half of tumors arise in the femur
- Of these, 80% are in the distal femur
Other primary sites in descending order of frequency are:
- Proximal tibia
- Proximal humerus
- Pelvis
- Jaw
- Fibula
- Ribs
Osteosarcoma of the head and neck is more likely to be low grade and to arise in older patients.
Extraskeletal osteosarcoma is rare, and there is controversy over whether this represents a true osteosarcoma or a variant of a soft tissue sarcoma.
Primary sites of origin osteosarcoma:
Femur |
50% |
Tibia |
25% |
Humerus |
10% |
Fibula |
about 5% |
Pelvis |
about 5% |
