Understanding Bone Cancer: What Is Bone Cancer?

To understand bone cancer, it’s first important to understand what cancer is: basically, the production of abnormal cells.

The body is programmed to routinely replenish cells in different organs. As normal cells age or get damaged, they die off. New cells take their place. This is what’s supposed to happen. Abnormal cell growth refers to a buildup of extra cells. This happens when:

  • New cells form even though the body doesn’t need them or
  • Old, damaged cells don’t die off.

These extra cells slowly accumulate to form a tissue mass, lump, or growth called a tumor. These abnormal cells can destroy normal body tissue and

About Bone Cancer

Your bones support your body. New bone is always forming while old bone is dissolving. Bone contains 2 kinds of cells:

  • Osteoblast is the cell that lays down new bone.
  • Osteoclast is the cell that dissolves old bone.

Most bones are hollow. They are filled with a soft spongy tissue called bone marrow. In some bones, the marrow is a combination of fat cells and blood-forming cells. These produce red blood cells, white blood cells, and blood platelets. Other cells in the marrow include plasma cells, fibroblasts, and reticuloendothelial cells.

Cells from any of these tissues can develop into a cancer.

Types of Bone Tumors

Bone cancer is different from other cancers because usually cancer doesn’t start in the bones. Usually when your doctor tells you that you have cancer in your bones, it is a cancer that has spread to the bones from somewhere else. This is called metastatic cancer. Breast, prostate, and lung cancers commonly spread to the bones. For example, if lung cancer has spread to your bones, the cells will still look like lung cancer cells under the microscope. They must be treated with lung cancer drugs.

Cancers that start in the cells of the bone marrow are sometimes called “bone cancers.” The most common type is multiple myeloma. Leukemia is another cancer that begins in the bone marrow. It is commonly called a blood cancer, not a bone cancer. In this piece, we focus only on primary bone cancer.

Understanding Primary Bone Cancer

Primary bone cancers are also called true bone cancers or sarcomas. These cancers start in bone, muscle, fibrous tissue, blood vessels, fat tissue as well as some other tissues. They can develop anywhere.

There are several different kinds of bone tumors. They are named according to:

  • The area of bone or surrounding tissue that is affected.
  • The kinds of cells that make up the tumor.

Most bone tumors are sarcomas. Some primary bone tumors are benign, and others are malignant.

Benign vs. Malignant: What’s the Difference?

Benign means not cancerous. A benign tumor can get larger but does not spread to other tissues or organs.

Malignant means cancerous. A malignant tumor’s cells can invade nearby tissue, lymph nodes and spread to other organs. These cells are destructive.

Benign tumors:

  • Can be removed
  • Usually don’t grow back
  • Are rarely fatal
  • Don’t spread to other tissues or body parts


Malignant tumors:

  • Can often be removed
  • Sometimes grow back
  • Can invade other tissues and organs and cause damage
  • Can spread to other body parts
  • Can be fatal

Benign Bone Tumors

Benign tumors do not spread to other tissues and organs and so are not usually life threatening. They are generally cured by surgery. Types of benign bone tumors include:

  • Osteoid osteoma
  • Osteoblastoma
  • Osteochondroma
  • Enchondroma
  • Chondromyxoid fibroma.

Malignant Bone Tumors

Osteosarcoma is the most common primary bone cancer. It starts in your bone cells. It usually affects people between the ages of 10 and 30. However, about 10% of osteosarcoma cases develop in people in their 60s and 70s. It is rare in middle aged people. It is more common in males than females. These tumors develop most often in bones of the arms, legs, or pelvis.

Chondrosarcoma is a cancer of cartilage cells. It is the second most common primary bone cancer. This cancer is rare in people under age 20. After age 20, the risk of getting a chondrosarcoma goes up until about age 75. Women get this cancer as often as men.

Chondrosarcomas can develop anywhere in your body that there is cartilage. Most develop in bones such as the pelvis, leg bone or arm bone. Occasionally, chondrosarcoma will develop in your:

  • Trachea
  • Larynx
  • Chest wall
  • Shoulder blade
  • Ribs
  • Skull

There are 2 types of cartilage tumors that are benign:

  • Enchondroma
  • Osteochondroma

These tumors seldom turn into cancer.

Chondrosarcomas are classified by grade, which measures how fast they grow. Most chondrosarcomas are either low grade (grade I) or intermediate grade (grade II). High grade (grade III) chondrosarcomas are the most likely to spread. Fortunately, they are also less common.

Ewing tumor: Ewing tumor is the third most common primary bone cancer. It is more common in children, adolescents, and young adults. It is also called Ewing sarcoma. This sarcoma is very rare in adults over age 30. Most of these tumors develop in bones, but they can start in other tissues and organs. This cancer most often develops in the pelvis, chest wall and long bones of the legs and arms.

Malignant fibrous histiocytoma (MFH) usually starts in soft tissue such as ligaments, tendons, fat and muscle. When it does occur in bones, it usually affects the legs or arms. Often it affects the knees. This cancer usually occurs in elderly and middle-aged adults. It is rare among children.

Fibrosarcoma develops more often in "soft tissues" than in bones. This cancer usually affects elderly and middle-aged people. Leg, arm, and jaw bones are the ones most often affected.

Giant cell tumor of bone can be either benign or malignant. The benign kind is more common. These tumors usually affect the leg, near the knees, or arms bones. It usually affects young and middle-aged adults. Giant cell tumors don’t usually spread but tend to come back after surgery. Sometimes, a giant cell bone tumor spreads to other parts of the body. When this happens, it is the malignant form of the tumor.

Chordoma typically occurs in the base of the skull and bones of the spine. It develops most often in adults older than 30. It is more common in men than in women. Chordomas tend to grow slowly and often do not spread to other parts of the body. If not removed completely, though, they can come back in the same area. When they do spread, they usually spread to the lymph nodes, lungs and liver.

Non-Hodgkin lymphomas and multiple myeloma are two other cancers that can develop in the bone.

Next: How is bone cancer diagnosed? 

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