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TNM stages for mouth cancer

The stage of mouth cancer tells you its size and depth, and whether it has spread. 

Doctors stage mouth cancers differently to cancers that start in the throat behind the mouth (oropharyngeal cancer). This page is about the TNM stages for cancers starting in the mouth. This includes cancers starting in the lips, gums, the soft sides of the mouth and the front part of the tongue.

Staging systems

Staging looks at the size and depth of the cancer (tumour) and whether it has spread anywhere else in the body. There are different staging systems doctors can use for mouth cancer. The TNM staging system is one of these.

TNM stands for Tumour, Node, Metastasis. It describes:

  • the size and depth of the primary tumour (T)
  • whether the cancer has spread to the lymph nodes (N)
  • whether the cancer has spread to another part of the body (M)

The TNM system is used for cancer staging all over the world. It is important for doctors to use the same staging system because then they can be sure they are all talking about the same situation when they are comparing notes or carrying out research.

Your doctor might also use a number staging system to describe the stage of your cancer.

How do doctors find out your stage?

Doctors find out the stage of your cancer by:

  • examining you and looking at test and scan results - this is called clinical staging
  • examining tissue that the surgeon removes during an operation - this is called pathological staging

Your doctor might use clinical staging if you don't have surgery straight away, or at all. They work out your stage after physically examining you and reviewing your test and scan results. But if you have surgery, doctors can also find out the pathological stage of your cancer. This is also called the surgical stage. So your stage might change if you have an operation. 

Sometimes, your pathological stage is different from your clinical stage. For example, the surgery might show that your cancer has spread further than the doctors first thought. So the pathological stage can be more precise. 

The TNM staging system described below uses the clinical stage.  But it is similar to the pathological staging system. 

Cancer staging is complicated so ask your doctor or specialist nurse to explain this to you if you need help to understand it.  

You can call the Cancer Research UK nurses on freephone 0808 800 4040, from 9am to 5pm, Monday to Friday.

Tumour (T)

T describes the size and depth of the tumour (area of cancer). 

There are 4 main T stages of mouth cancer. These are T1 to T4.

T1 means the cancer is contained within the tissue of the mouth (oral cavity) and it is:

  • 2cm or smaller
  • 5mm deep or less

T2 can mean different things.

The cancer is 2cm or smaller, and it is deeper than 5mm but no deeper than 10mm.

 Or the cancer is larger than 2cm, but no larger than 4cm, and it is 10mm deep or less.

T3 means the cancer is larger than 4cm, or deeper than 10mm

T4a means the cancer has grown further than the mouth and into surrounding structures such as bone, skin or the facial air cavities (sinuses).

T4b means the cancer has spread into nearby areas such as the space behind the jaw, the base of the skull, or the area of neck surrounding the arteries (carotid arteries).

Node (N)

N refers to your lymph nodes. These are a network of glands throughout the body, for example in your armpits and neck. They drain away waste fluid, waste products and damaged cells, and contain cells that fight infection. 

The important points here are:

  • whether any nodes contain cancer
  • the size of the node containing cancer
  • which side of the neck the node containing cancer is on
  • whether the cancer has spread into the tissue surrounding the lymph node

There are 4 main N stages of mouth cancer. These are N0 to N3.

N0 means the lymph nodes don’t contain cancer cells. 

N1 means that one lymph node contains cancer cells on the same side of the neck as the cancer. The node is no larger than 3cm across. The cancer has not spread into tissue surrounding the lymph node.

N2 is split into 3 groups - N2a, N2b and N2c.

N2a means one lymph node contains cancer cells on the same side of the neck as the cancer. The node is between 3cm and 6cm across. The cancer has not spread into tissue surrounding the lymph node.

N2b means that more than one lymph node contain cancer cells on the same side of the neck as the cancer. None of these nodes are more than 6cm across. The cancer has not spread into tissue surrounding the lymph node.

N2c means there are cancer cells in lymph nodes on the other side of the neck to the cancer, or in nodes on both sides of the neck. None of these nodes are more than 6cm across. The cancer has not spread into tissue surrounding the lymph node.

N3 is split into 2 groups - N3a and N3b.

N3a means that one lymph node that contains cancer cell is larger than 6cm across. The cancer has not spread into tissues surrounding the lymph node.

N3b means any number of lymph nodes contain cancer. The cancer has spread into tissues surrounding the lymph node.

Metastasis (M)

M describes whether the cancer has spread to a different part of the body.

There are 2 main stages - M0 and M1.

M0 means the cancer has not spread to other parts of the body

M1 means cancer has spread to other parts of the body such as the lungs 

Treatment

The stage of your cancer helps your doctor to decide which treatment you need. Treatment also depends on:

  • your type of cancer (the type of cells the cancer started in)
  • where the cancer is 
  • other health conditions that you have

The stage of the cancer and these other factors can also give an idea of your outlook (prognosis).

Treatment may include

  • surgery
  • radiotherapy
  • chemotherapy
Last reviewed: 
08 May 2019
  • AJCC Cancer Staging Manual, 8th Edition
    American Joint Commitee on Cancer, 2017

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