Osteocarcoma is the most common type of bone cancer, usually diagnosed in teenagers and young adults.
It occurs when the cells that grow new bone form a cancerous tumor.
The cause of the cancer is unknown but it is thought to be related to rapid bone growth, such as adolescence.
Most tumors usually develop around the knee either in the lower part of the thighbone or the upper part of the shinbone.
Rarely, some bone cancers may occur in people from families where there is an inherited faulty gene that increases the risk of developing several types of cancer (Li-Fraumeni syndrome).
If the cancer has not spread, the long-term survival rate is between 70 and 75