Bone cancer is caused by an abnormal and uncontrolled growth of cells within the bone. It can be benign or malignant.
Benign tumours aren't cancerous. They don't spread to other parts of the body and don't invade surrounding tissue.
Malignant tumours are cancerous. They spread to other parts of the body and invade surrounding tissue. This spread of cancer is called a metastasis and can form a secondary cancer in another organ.