The stage of a cancer describes its size and whether it has spread. Knowing the extent of the cancer helps the doctors to decide on the most appropriate treatment for you.

Doctors often use scans to assess the stage of a cancer. This is called clinical staging. But your doctor may only be able to tell you the exact stage of the cancer after you have had an operation to remove it.

The most commonly used staging system for stomach cancer is called the TNM system:

T refers to the size of the tumour.
N refers to whether lymph nodes have cancer in them.
M refers to whether the cancer has spread to other parts of the body (secondary or metastatic cancer).

You may find it useful to look at our diagram of the stomach wall 

Tumour size (T)

• T1 The cancer has not grown beyond the inner layer of the stomach.  
• T2 The tumour has grown into the muscle layer of the stomach.  
• T3 The tumour has grown beyond the outer layer (serosa) of the stomach. 
• T4 The tumour has spread to structures nearby the stomach such as the gullet, liver or abdominal wall.

Lymph nodes (N)The N refers to whether the cancer cells have spread into the lymph nodes close to the stomach. The lymph node stages are:

• N0 There are no cancer cells in any lymph nodes. 
• N1 There are cancer cells in up to 6 lymph nodes.
• N2 There are cancer cells in between 7 and 15 lymph nodes. 
• N3 There are cancer cells in more than 15 lymph nodes.If cancer cells have spread to the lymph nodes, the nodes are said to be positive.

Metastases (M)

• M0 the cancer cells have not spread elsewhere in the body. 
• M1 the cancer cells have spread to other parts of the body.This is called secondary or metastatic stomach cancer.

The T, N and M stages may be grouped together to give an overall stage for the cancer from 1–4.

Stage 1A The cancer is contained within the inner lining of the stomach (mucosa) only.

Stage 1B The cancer has grown into the muscle layer of the stomach, OR it is affecting up to six of the nearby lymph nodes.

Stage 2 The cancer has spread through the mucosa and is affecting between 7 and 15 lymph nodes nearby, OR it is affecting the muscle layer and up to six lymph nodes, OR it has spread to the outer layer of the stomach (serosa).

Stage 3A The cancer has spread to the muscle layer of the stomach and also to between 7 and 15 lymph nodes nearby, OR it has spread to the outer layer of the stomach and is affecting up to six lymph nodes, OR it has spread to structures close to the stomach but not to any lymph nodes or any other parts of the body.

Stage 3B The cancer has spread to the serosa and it is also affecting between 7 and 15 lymph nodes.

Stage 4 The cancer has spread to organs close to the stomach and to at least one lymph node, OR to more than 15 lymph nodes, OR it has spread to other parts of the body such as the lungs.

The grade of a cancer gives an idea of how quickly it may develop. To find the grade of the cancer, your doctors will look at a sample of the cancer (a biopsy) under the microscope.

Grade 1 (low grade) – the cancer cells tend to be slow growing, look quite similar to normal cells (are ‘well differentiated’) and are less likely to spread. 

Grade 2 (moderate grade) – the cells look more abnormal. 

Grade 3 (high grade) – the cancer cells tend to be more quickly growing, look very abnormal (are ‘poorly differentiated’) and are more likely to spread than low-grade cancers.