1. Definition
The word "tumor" is the Latin word for "swelling." Simply put, tumors are growths that occur where they are not supposed to.
2. Benign or Malignant
There are benign tumors and malignant tumors. These refer to the types of cells that are present in the tumor itself. Malignant tumors are cancerous because the cells themselves are abnormal. Benign tumors contain normal cells--just more of them than usual. This takes up space, which can put pressure on other structures, such as blood vessels and nerves. It can also take up space within bones, which can weaken bone structure and cause pain. Benign bone tumors include non-ossifying fibromas, osteochondromas (exostoses), enchondromas (made of cartilage), giant cell tumors and fibrous dysplasia.
3. Primary Bone Tumors
Primary bone cancers are rare, and arise from the bone itself, not from a distant site (metastasis). They must arise from elements found in the bone. One common primary bone tumor is multiple myeloma, which arises from the bone marrow elements. It is a cancer of the white blood cell line (immune system), and usually occurs in older patients. Another primary bone cancer is osteosarcoma. This is a cancer of the cells (osteoblasts) that produce bone, commonly around the knee (femur and tibia). This condition has a bimodal distribution. Most occur in children and teenagers, but there is another peak of occurrences in the elderly. Ewing's sarcoma occurs in children and teenagers. Chondrosarcomas arise from cartilage cells that become malignant. This occurs in the elderly, usually around the pelvic area.
4. Metastases
Cancers arising from bone itself are fairly rare, but cancers that spread to the bones are quite common. Cancers can develop in other organs and break off (metastasize) to distant locations through the blood. Because the bones have very good circulation, cancers cells can deposit themselves in bone and continue to grow. Cancers that commonly spread to bone include prostate, thyroid, breast, lung and kidney.
5. Pain and Fractures
Tumors can be benign but locally aggressive. Giant cell tumors of the bone are by definition benign because of the benign cells contained within the mass. However, it can grow and weaken bones. Metastases are aggressive and can eat away the bone. Either way, the bone can become thin and cause pain. Usually, an X-ray will be able to detect the abnormalities. If the bone weakens enough, it can fracture. These types of fractures are called pathologic fractures. They occur from forces that are not usually sufficient to break bones. But once the bone is weaker, it breaks more easily. One example is getting a shoulder fracture simply from being pulled up from a couch. Pathologic fractures secondary to tumors are difficult to treat, and may require surgery with rods inside the bones; some may require prosthetic replacement.
