- the grade of the cancer – how the cancer cells look under the microscope. This gives and idea of how quickly a cancer may grow and develop.
- the stage of the cancer - its size and whether it has spread outside the bone.
The grading and staging of primary bone cancer is complex. Your cancer doctor and specialist nurse will talk to you about this. They will explain how it helps you and your cancer doctor decide on a treatment plan that is right for you.
A doctor decides the grade of the cancer by looking at the cancer cells under a microscope. The grade gives an idea of how quickly the cancer might grow or develop.
The most common grading system for primary bone cancer uses 2 grades:
- Low-grade tumours
The cancer cells look like normal bone cells. They are usually slow-growing and are less likely to spread.
- High-grade tumours
The cells look very abnormal. They are likely to grow more quickly and are more likely to spread.
Chondrosarcomas are graded from 1 to 3. Grade 1 is low-grade cancer and grade 3 is high-grade cancer.
The stage of a primary bone cancer describes its size and whether it has spread outside the bone. Knowing the stage of the cancer helps the doctors plan the right treatment.
Most cancers are grouped depending on whether they:
- are only in one part of the body (localised)
- have spread from one part of the body to another (secondary or metastatic).
If the cancer comes back after it is first treated, doctors call it a recurrence.
There are different staging systems used for primary bone cancer. The most-used systems are TNM and Enneking.
TNM staging system
TNM stands for Tumour, Node and Metastases:
- T - describes the size of the tumour.
- N - describes whether the cancer has spread to lymph nodes.
- M - describes whether the cancer has spread to another part of the body (called metastatic or secondary cancer).
Enneking staging system
As well as the size of the tumour and if it has spread, the Enneking staging system also describes the grade of the cancer. It helps your surgeon decide how much bone to remove during surgery.
Stage 1 bone cancer is low-grade. It has not spread beyond the bone. Stage 1 is divided into:
- Stage 1A - The cancer is completely inside the bone it started in. The cancer may be pressing on the bone wall and causing a swelling, but it has not grown through it.
- Stage 1B - The cancer has grown through the bone wall.
Stage 2 bone cancer is high-grade. It has not spread beyond the bone. Stage 2 is divided into:
- Stage 2A - The cancer is completely inside the bone it started in.
- Stage 2B - The cancer has grown through the bone wall.
Stage 3 bone cancer may be any grade. It has spread to other parts of the body, such as the lungs.