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 numbers to describe the cancer.
**T refers to the size of the cancer and how far it has spread into nearby tissue88 – it can be 1, 2, 3 or 4, with 1 being small and 4 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.
Sometimes the letters a, b or c are used to further divide the categories. For example, stage M1a lung cancer (the cancer has spread to the other lung) and stage M1b lung cancer (the cancer has spread to other parts of the body).
The letter p (pathological stage) is sometimes used before the letters TNM – for example, pT4. It means that the stage is based on examining cancer cells in the lab after surgery to remove a cancer.
The letter c (clinical stage)) is sometimes used before the letters TNM – for example, cT2. It means the stage is based on what the doctor knows about the cancer before surgery. The stage is based on clinical information from examining you and looking at your test results.