Classification of stage of gastric cancer

Tumour (T)

Tumour describes the size of the tumour.

There are 4 main stages of tumour size in stomach cancer.

T1 means the tumour has started to grow into the wall of the stomach. It’s divided into T1a and T1b:

• T1a means the tumour is within the inner layers of the stomach (the mucosa)
• T1b means the tumour has grown through the mucosa and into a layer of supportive tissue called the submucosa

T2 means the tumour has grown into the muscle layer of the stomach

T3 means the tumour has grown into the outer lining of the stomach

T4 means that the tumour has grown through the outer lining of the stomach. It’s divided into T4a and T4b:

• T4a means the tumour has broken through the outer lining of the stomach wall
• T4b means the tumour has grown through the stomach wall and into other organs or body structures nearby such as the liver, food pipe (oeosphagus) or abdominal wall

Node (N)

Node (N) describes whether the cancer has spread to the lymph nodes. Lymph nodes are a network of glands throughout the body, for example in your armpits, neck and groins. They drain away waste fluid, waste products and damaged cells, and contain cells that fight infection.

There are 4 possible stages describing whether cancer cells are in the lymph nodes – N0, N1, N2 and N3:

N0 means there are no lymph nodes containing cancer cells.

N1 means there are cancer cells in 1 to 2 lymph nodes near to the stomach.

N2 means there are cancer cells in 3 to 6 nearby lymph nodes.

N3 is split into N3a and N3b:

• N3a means there are cancer cells in 7 to 15 nearby lymph nodes
• N3b means there are cancer cells in 16 or more nearby lymph nodes

Metastasis (M)

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

There are 2 stages of metastasis:

• M0 means the cancer has not spread to other organs
• M1 means the cancer has spread to other parts of the body