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The bones

 Men and women discussing bone cancer

This page tells you about the bones and about the difference between cancer that starts in the bones (primary bone cancer) or that spreads into the bone from another part of the body (secondary bone cancer).

 

A quick guide to what's on this page

The bones

There are more than 200 bones in the human body. Bones support and protect the body, as well as allowing us to move. 

Bone is a framework made of supporting tissue, called connective tissue. Bone contains minerals such as calcium. This framework gives the bone its strength. Throughout the framework are the bone cells.

There are 3 main types of cells in our bones 

  • Osteoblasts – build up the bone framework
  • Osteoclasts – break down bone 
  • Osteocytes – are osteoblasts that have become part of the bone framework 

These cells all work together to keep your bones healthy and maintain their shape.

Primary bone cancer

Primary bone cancer is cancer that has started in the cells of the bones. There are several different types of primary bone cancer.

Cancer that has spread to the bones (secondary bone cancer)

Most people with cancer in their bones have cancer that has spread there from another part of the body. The cancer may have started in the breast, for example. Breast cancer cells have travelled to the bones and started to grow there. This is called secondary bone cancer. If you have secondary bone cancer this is not the right section for you. You need to look at the section for your primary cancer.

 

CR PDF Icon You can view and print the quick guides for all the pages in the About bone cancer section.

 

 

The skeleton

There are more than 200 bones in the human body. The bones

  • Support the body
  • Protect parts of the body
  • Act as levers and allow us to move

Diagram of the skeleton

The long bones of the arms and legs are supporting bones. The bones of the rib cage protect the organs of the chest. The skull bones protect the brain.

The end of every long bone in the body is covered in a smooth, shiny tissue called cartilage. Fibrous straps called tendons hold the long bones together. The tendons and cartilage make joints that allow the bones to move smoothly against each other.

 

The bone cells

Bone is a framework of supporting tissue, called connective tissue. Bone contains minerals such as calcium. This framework gives the bone its strength. Throughout this framework are the bone cells.

Diagram of an osteocyte - a type of bone cell

There are 3 main types of cells in our bones

  • Osteoblasts – build up the bone framework
  • Osteoclasts – break down bone
  • Osteocytes – are osteoblasts that have become part of the bone framework

These cells work together to maintain the shape, strength and health of the bones. If a bone gets damaged, the osteoblasts make new bone to repair the damage. The osteoclasts break down any extra bone framework that the osteoblasts make. When bone forms, osteoblasts are trapped within it and become part of the framework. They are then called osteocytes. Osteocytes are involved in maintaining the bone structure.

Inside some of the bones of the body is a space that is filled with bone marrow. The bone marrow is where blood cells are made. All blood cells develop from stem cells which are found in the bone marrow.

 

Cancer that starts in the bones – primary bone cancer

Primary bone cancer is cancer that has started in the cells of the bones. There are several different types of primary bone cancer, including

  • Osteosarcoma
  • Chondrosarcoma
  • Ewing's sarcoma
  • Spindle cell sarcoma
  • Chordoma

Primary bone cancers are extremely rare. The most common types of bone cancer diagnosed in children and teenagers are osteosarcoma and Ewing's sarcoma. Chondrosarcoma is the most common type diagnosed in middle aged and older people. There is more information about the different types of bone cancer in this section.

A type of cancer called myeloma can affect the bones, and people sometimes call it bone cancer. But it is not a type of primary bone cancer because it does not start in the bone itself. Myeloma develops from cells in the bone marrow called plasma cells. So it can develop anywhere there is bone marrow, including the pelvis, spine and ribcage. If you want to read about myeloma, there is more information in the myeloma section.

When a primary bone cancer starts to grow, the cancer cells multiply and begin to break down the bone. This weakens the bone in that area. Bone cancer cells can break away from the primary bone tumour and travel to other bones, the lungs or other body organs. There they can grow into secondary tumours.

 

Cancer that has spread into the bone – secondary bone cancer

Most people who have cancer cells in their bones actually don't have primary bone cancer. They have cancer cells that have spread into the bone from a cancer elsewhere in the body. This is called secondary cancer. Cancer that has spread from where it started in the body is also called metastatic cancer. Nearly all types of cancer can spread to the bones. Common cancers that spread to the bones include breast cancer, lung cancer, prostate cancer and kidney cancer. So if you have bone cancer that is secondary to breast cancer, the cancer cells in your bones are breast cancer cells.

The type of primary cancer you have is very important. Cancers respond to treatment according to the type of primary cancer. So breast cancer in the bones will respond to treatments for breast cancer.

If you have secondary bone cancer, this is not the right section for you. You need to look at the section for your type of primary cancer – named after the place in your body where your cancer started.

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Updated: 17 December 2014