Types of staging systems
There are 2 main types of staging systems for cancer—these are the TNM system and the number system.
The systems mean that doctors have a common language to describe the size and spread of cancers. Some blood cancers or lymph system cancers have their own staging systems.
TNM stands for Tumour, Node, Metastasis. This system describes the size of the initial cancer (the primary tumour), whether the cancer has spread to the lymph nodes, and whether it has spread to a different part of the body (metastasised). The system uses letters and numbers to describe the cancer:
- T refers to the size of the cancer and how far it has spread into nearby tissue – it can be 1, 2, 3 or 4, with 1 being small and 4 being large.
- N refers to whether the cancer has spread to the lymph nodes – it can be between 0 (no lymph nodes containing cancer cells) and 3 (lots of lymph nodes containing cancer cells).
- M refers to whether the cancer has spread to another part of the body – it can either be 0 (the cancer hasn’t spread) or 1 (the cancer has spread).
So, for example, a small cancer that has spread to the lymph nodes but not to anywhere else in the body may be T2 N1 M0. Or a more advanced cancer that has spread may be T4 N3 M1.
Most types of cancer have 4 stages, numbered from 1 to 4. Often doctors write the stage down in Roman numerals. So you may see ‘stage 4’ written down as ‘stage IV’.
Here is a brief summary of what the stages mean for most types of cancer:
Stage 1 – usually means that a cancer is relatively small and contained within the organ it started in.
Stage 2 – usually means that the tumour is larger than in stage 1, but the cancer has not started to spread into the surrounding tissues. Sometimes stage 2 means that cancer cells have spread into lymph nodes close to the tumour. This depends on the particular type of cancer.
Stage 3 – usually means the cancer is larger. It may have started to spread into surrounding tissues and there are cancer cells in the lymph nodes in the area.
Stage 4 – means the cancer has spread from where it started to another body organ. This is also called secondary or metastatic cancer.