TNM stages for mouth cancer

The stage of mouth cancer tells you how big it is, its depth, and whether it has spread. It helps your doctor decide the best treatment for you.

TNM system stands for Tumour, Node and Metastasis. It is the most common way to stage mouth cancer. Doctors may also use the number system.

Doctors stage mouth cancers differently from cancers that start in the throat behind the mouth (oropharyngeal cancer).

How do doctors find out your stage?

There are different ways to find out your stage. Your doctor might use:

• clinical staging before treatment and if you don't have surgery
• pathological staging if you do have surgery

Clinical staging means the doctor stages you after examining you and looking at test and scan results. Doctors use clinical staging to plan your treatment. It’s also the best way to stage people who aren’t having surgery. You might see your clinical stage written as cTNM.

Pathological staging means the doctor stages you after examining the tissue that the surgeon removes during an operation. This is also called surgical staging. The doctors combine your clinical stage results with the surgical results. Pathological staging is generally a more precise way to find out how far your cancer has spread. Your pathological stage might be different to your clinical stage. You might see your pathological stage written as pTNM.

Pathological staging is different from clinical staging for mouth cancer. For example, pathological staging looks at the number of lymph nodes containing cancer rather than their size.

We describe the clinical stage below. This is because not everyone with mouth cancer has surgery to stage their cancer, so doctors don't always know the pathological stage.  

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

Tumour (T)

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

TX means the main cancer (primary) can’t be assessed.

Tis means the cancer cells are in the top layer of cells lining the lips or mouth.

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 one of the following:

• the cancer is 2cm or smaller, and it is deeper than 5mm but no deeper than 10mm
• the cancer is larger than 2cm but no larger than 4cm, and it is 10mm deep or less

T3 means one of the following:

• the cancer is larger than 4 cm, and it is 20mm deep or less
• the cancer is any size, and it is 20mm deep or less

T4a means the cancer has grown further than the mouth and into surrounding structures such as the jaw bones, the skin of the face or the air filled spaces in the skull (sinuses) or the tongue. This is also called moderately advanced local disease.

T4b means the cancer has spread into the space behind the jaw, other nearby bones or the base of the skull or has surrounded a large blood vessel called the carotid artery. This is also called very advanced local disease.

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. 

When looking at your lymph nodes, your doctor keeps the following in mind:

• whether any nodes contain cancer
• the size of the node containing cancer
• which side of the neck the node containing cancer is in
• whether the cancer has spread into the tissue surrounding a lymph node (extranodal extension or ENE)  

NX means the lymph node can’t be assessed.

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 the 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 the tissue surrounding the lymph node.

N2b means that more than one lymph node contains 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 the 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 the 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.

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 for mouth cancer may include

• surgery
• radiotherapy or chemoradiotherapy after surgery
• chemotherapy
• a targeted cancer drug
• immunotherapy

If you have early stage lip cancer, you may have surgery or radiotherapy as your main treatment.