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Number stages and grades of mouth cancer

The stage of mouth cancer tells you its size and depth, and whether it has spread. The grade tells you how much the cancer cells look like normal cells. This gives your doctor an idea of how the cancer might behave and what treatment you need. 

Doctors stage mouth cancers differently to cancers that start in the throat behind the mouth (oropharyngeal cancer). This page is about the number 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

There are different ways of staging mouth cancer. These are the number staging system and the TNM system.

The Number staging system divides mouth cancer into 4 main stages, from 1 to 4. Stage 1 is an early cancer and stage 4 is an advanced cancer. Some doctors also use stage 0. 

Doctors might also use the TNM staging system.

Stage 0 or carcinoma in situ (CIS)

Stage 0 cancer or carcinoma in situ (CIS) means your cancer is at a very early stage. Some doctors prefer to call this pre cancer. There are cancer cells but they are all contained within the lining of the mouth or oropharynx. The cancer cells have not spread.

If the pre cancer is not treated, there is a high risk the condition will develop into an invasive cancer. 

Stage 1

This is the earliest stage of invasive cancer. 

It means the cancer is 2cm or smaller and it is 5mm deep or less. It has not spread to nearby tissues, lymph nodes or other organs.

In the TNM staging system stage 1 mouth cancer is the same as T1, N0, M0.

Stage 2

Stage 2 can mean different things including:

  • 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

The cancer has not spread to nearby lymph nodes or other organs.

In the TNM staging system stage 2 mouth cancer is the same as T2, N0, M0

Stage 3

Stage 3 means one of the following;

  • the cancer is larger than 4cm, or deeper than 10mm, but has not spread to any lymph nodes or to other parts of the body
  • the cancer is any size but one lymph node contains cancer cells on the same side of the neck as the cancer, and the lymph node is no more than 3cm across

In the TNM staging system stage 3 mouth cancer is the same as one of the following:

  • T3, N0, M0
  • T1,2 or 3, N1, M0

Stage 4

Stage 4 means the cancer is advanced. It is further divided into 3 stages - 4a, 4b and 4c.

Stage 4a 

Stage 4a can mean different things, including:

  • the cancer has grown further than the mouth into surrounding structures
  • cancer has spread to lymph nodes on either side of the neck, which are between 3 and 6 cm in size
  • cancer has spread into one nearby lymph node which is no larger than 3cm and it has also spread into tissue surrounding the lymph node

In the TNM staging system stage 4a mouth cancer is the same as one of the following:

  • T4a, N0 or 1, M0
  • T1,2,3 or 4a, N2, M0

Stage 4b

Stage 4b can mean different things, including:

  • 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)
  • a lymph node containing cancer is larger than 6cm 
  • cancer has spread into tissues surrounding the lymph node

In the TNM staging system stage 4b mouth cancer is the same as one of the following:

  • any T, N3, M0
  • T4b, any N, M0

Stage 4c

Stage 4c means the cancer has spread to other parts of the body such as the lungs or bones.

In the TNM staging system stage 4c mouth cancer means:

  • any T, any N, M1

Grades of mouth cancer

The grade of a cancer tells you how much the cancer cells look like normal cells. This gives your doctor an idea of how the cancer might behave and what treatment you need. 

There are 3 grades of mouth cancer:

  • grade 1 (low grade) means cancer cells look like normal mouth cells
  • grade 2 (intermediate grade) look slightly different to normal mouth cells
  • grade 3 (high grade) look very abnormal and not much like normal mouth cells 

Your cancer might be graded as Gx. This means that the grade cannot be assessed.

Differentiation

Differentiation means how developed or mature a cell is. Doctors might describe cancer as poorly or well differentiated. 

Doctors might describe:

  • grade 1 cancer as well differentiated
  • grade 2 cancer cells are moderately differentiated
  • grade 3 cancer cells are poorly differentiated

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

Treatment might include:

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

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