Primary Bone Cancer
Some bone cancers occur in the form of cancerous cells derived from the bones. There are a wide variety of these kinds of tumors. They include tumors of the bone tissue (osteosarcoma), tumors of the cartilage (chondrosarcoma), tumors of the ligaments and connective tissue (malignant fibrous histiocytoma), and tumors that start at the base of the skull and spine (chordoma). These types of bone cancers cause pain at the site of the tumors, as well as swelling and redness. Because the normal bone tissue is replaced with cancerous tissue, the bones become weak and are more likely to fracture. Bone cancers of this type tend to sap a lot of the body's energy and resources, leading to extreme fatigue and unintended weight loss.
Another kind of bone cancer begins in the bone marrow, which is where the red blood cells are made. Multiple myeloma is the only form of bone marrow cancer that is considered medically to be a cancer of the bone, not simply of the blood. This is because multiple myeloma cells are able to proliferate throughout the bones. Aside from bone pain and bone weakness (a result of normal bone cells being replaced with cancer), multiple myeloma can cause your immune system to become weak as it stops producing viable white blood cells. Multiple myeloma can also cause kidney failure because the kidneys become overworked by trying to clear abnormal proteins out of the blood (which are created by the cancer).
Another way in which the bones can develop cancer is via a process known as metastasis. Metastasis occurs when cancer from one part of the body spreads to other areas, which can include the bones. Breast cancer, lung cancer and prostate cancer all have a tendency to spread to the bones. Metastatic bone cancer causes the same bone pain and weakness of other forms of bone cancer, as well as fatigue and weight loss.