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The stages of bone cancer

The stage of a cancer is important when deciding on treatment. The most commonly used staging system for bone cancer in the UK is the Enneking system. The Enneking system is based on the tumour grade, site, and whether or not the cancer has spread to other parts of the body (metastasised).

The Enneking system divides bone cancers into 3 stages – stages 1 to 3.

  • Stage 1 means the cancer is low grade
  • Stage 2 means the cancer is high grade
  • Stage 3 means that the cancer has spread to another part of the body (metastasised)

The TNM system is based on the tumour size, whether cancer cells have spread into nearby lymph nodes, and whether there are metastases. The TNM system is used to create 4 number stages from 1 to 4.

  • Stage 1 means low grade cancer
  • Stage 2 means high grade cancer
  • Stage 3 means there is more than one area of cancer in the primary site
  • Stage 4 means that the cancer has spread to another part of the body such as the lung

Some doctors may refer to stage 0. Stage 0 means carcinoma in situ, which is a very early cancer that has not spread.

The grade of bone cancer cells

Doctors grade bone cancer cells according to how the cells look under a microscope. In low grade cancers, the cells look very like normal cells and tend to grow slowly. High grade cancers tend to grow more quickly and are more likely to spread.

 

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

 

 

What staging is

The stage of a cancer tells the doctor how big it is and whether it has spread. This information is important because treatment is often decided according to the stage of a cancer. The tests and scans you have when diagnosing your cancer may give some information about the stage. In bone cancer, staging takes into account how abnormal the cells look under the microscope (the grade). 

The most commonly used staging system for bone cancer in the UK is the Enneking system. There is another staging system called the TNM system. There is detailed information about staging cancers in the section about cancer.

 

The grade of bone cancer cells

Doctors grade cancer cells according to how the cells look under a microscope. The grade of the bone cancer gives your specialist a guide to how the cancer may behave. Low grade cancers have cells that look slightly abnormal. These cancers usually grow slowly and are less likely to spread. High grade cancers have cells that look very abnormal. These cancers are likely to grow more quickly and are more likely to spread.

In the TNM system bone cancer cells are graded from GX to G4.

  • GX means the grade cannot be assessed
  • Grades 1 and 2 are low grade tumours
  • Grades 3 and 4 are high grade tumours

All Ewing's sarcomas are high grade (G4).

You may hear your doctor use the word differentiation. Differentiation means how developed or mature a cell is. So grade 1 cancer cells are well differentiated and look very like normal cells. Grade 2 cancer cells are moderately differentiated. Grade 3 cancer cells are poorly differentiated and look very abnormal. If a cancer cell is completely undifferentiated (grade 4) it may not be possible to tell what type of cell it originally was. 

There is detailed information about grade in the about cancer section.

 

The Enneking staging system for bone cancers

The Enneking system is a surgical staging system. Your surgeon uses it to decide how much bone to remove when they operate on the cancer.

The Enneking system is based on

  • Grade (G)
  • The site of the cancer in the bone (T)
  • Metastases (M) – whether the cancer has spread to another part of the body

In the Enneking system bone cancer tumours are graded from G0 to G2.

  • G0 means a non cancerous (benign) tumour
  • G1 means low grade cancer
  • G2 means high grade cancer

The Enneking system divides bone cancers into 3 stages – from 1 to 3.

  • Stage 1 means the cancer is low grade
  • Stage 2 means the cancer is high grade
  • Stage 3 means that the cancer has spread to another part of the body (metastasised)

Stages 1 and 2 are divided into A and B.

Stage 1 bone cancer

Stage 1A means low grade bone cancer that is still completely inside the bone in which it started. The tumour may press on the bone wall and cause swelling. But the cancer has not grown through the bone wall or spread to any other part of the body. This is called an intracompartmental bone cancer.

 

Bone cancer stage 1A

 

Stage 1B bone cancer is low grade but has grown through the bone wall. It is called an extracompartmental bone cancer. This means the cancer has grown out of the area (compartment) of the bone in which it started.

 

Bone cancer stage 1B

 

Stage 2 bone cancer

Stage 2A means the cancer is high grade but still completely within the bone in which it started. It has not spread to other areas of bone or any other part of the body. It is an intracompartmental cancer.


Bone cancer stage 2A

 

Stage 2B cancers are high grade and have grown through the wall of the bone into nearby tissues. They are extracompartmental cancers. This means they have grown out of the area (compartment) of bone in which they started.

 

Bone cancer stage 2B

 

Stage 3 bone cancer

A stage 3 bone cancer has spread to other bones or another area of the body. The most common area for bone cancer to spread to is the lungs. The second most common area for it to spread to is other bones.

Bone cancer stage 3

 

The TNM stages of bone cancer

After your cancer has been removed your surgeon sends it to the lab so a pathologist can look at the cells. In the TNM system all the information from your tests and scans is put together to give the stage. 

TNM stands for Tumour, Node and Metastasis. The system describes

  • The size of your primary tumour (T)
  • Whether the cancer has spread to the lymph nodes (N)
  • Whether the cancer has spread to a different part of the body – metastasised (M)

T (tumour) is divided into

  • T1 – tumours that are 8 cms or less at their widest point
  • T2 – tumours that are more than 8 cms
  • T3 – high grade tumours where there is more than one area of cancer in the same bone

N (node) is divided into

  • N0 – there are no cancer cells in lymph nodes close to the tumour
  • N1 – there are cancer cells in nearby lymph nodes

M (metastasis) is divided into

  • M0 – the cancer has not spread to any other part of the body
  • M1a – the cancer has spread to the lung
  • M1b – the cancer has spread to other areas of the body apart from the lung
 

The number stages of bone cancer

The tumour, node and metastasis results are put together with the grading to give the number stage. 

  • Stage 0 means carcinoma in situ – a very early, small, low grade cancer that has not spread
  • Stage 1A means a low grade tumour less than 8 cms across
  • Stage 1B means a low grade tumour more than 8 cms across or is in more than one place in the same bone
  • Stage 2A means a high grade tumour less than 8 cms across with no lymph nodes affected and no metastases
  • Stage 2B means a high grade tumour more than 8 cms across with no lymph nodes affected and no metastases
  • Stage 3 means a high grade tumour in more than one place on the same bone
  • Stage 4A means any size or grade of tumour that has spread to the lung
  • Stage 4B means any size or grade of tumour that has spread to the lymph nodes and/or a part of the body other than the lung

 

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Updated: 23 May 2013