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Stages of small bowel neuroendocrine tumours

The stage of a small bowel NET tells you how big it is and whether it has spread. The tests and scans you have when diagnosing your NET give information about the stage.

Your treatment depends on the stage of your tumour.

There are different ways to stage small bowel NETs. Doctors can use the TNM system or number system.

What are small bowel NETs?

Small bowel NETs are those that have started in the:

  • jejunum
  • ileum

Doctors group NETs that start in the duodenum differently.

Diagram showing the parts of the small bowel

TNM stage

In the UK, doctors usually use a staging system called TNM. TNM stands for tumour, node and metastasis:

  • T describes the size of the tumour
  • N describes whether there are any cancer cells in the lymph nodes
  • M describes whether the tumour has spread to a different part of the body

Tumour (T)

Tumour describes the size of the tumour (area of the cancer). 

Tx stage

Tx means the main tumour (primary) can’t be assessed.

T0 stage

T0 means there is no evidence of the main tumour (primary).

T1 stage

The tumour is no bigger than 1cm. It has grown into the inner lining of the small intestines (the mucosa) or into the next layer, the submucosa.

T2 stage

The tumour has grown into the muscle layer of the bowel wall. Or the tumour is bigger than 1cm.

T3 stage

The tumour has grown through the muscle layer and into the first part of the outer lining of the bowel wall.

T4 stage

The tumour has grown through the outer lining of the bowel wall. Or into a nearby organ or structure.

Diagram showing T-stages of bowel neuroendocrine tumours

Node (N)

The N stage describes whether the cancer has spread to the lymph nodes. There are 3 categories:

Nx stage

Nx means that the lymph nodes cannot be assessed.

N0 stage

N0 means there are no lymph nodes containing NET cells.

N1 stage

N1 means there are NET cells in the nearby lymph nodes. 

Diagram showing N1 stage for NET of the pancreas

Metastasis (M)

The M stage describes whether the tumour has spread to a different part of the body. There are 3 categories:

Mx stage

Mx means that doctors can’t assess whether the tumour has spread to a different part of the body.

M0 stage

M0 means the cancer has not spread to other areas of the body.

M1 stage

M1 means the cancer has spread to other areas of the body, such as the liver.

Diagram showing M1 stage for NET of the pancreas

Number stage

Your doctor might tell you the number stage of your NET. This system divides small bowel NETs into 4 main groups, depending on the size of the tumour and whether it has spread.

This is the earliest stage. It means the tumour is less than 1cm and is contained within the small bowel. In the TNM staging, this is the same as T1, N0, M0.

This means the tumour is contained within the small bowel.

Stage 2a
The tumour has grown into the muscle layer. Or the tumour is bigger than 1cm. In TNM staging, this is the same as T2, N0, M0.

Stage 2b
The tumour has grown into the thin layer of tissue in the small bowel wall called the subserosa. In TNM staging, this is the same as T3, N0, M0.

This means the tumour is not contained within the small bowel.

Stage 3a
The tumour has grown into the peritoneum (sheet of body tissue that lines the abdominal cavity and other organs inside it). Or it has grown into other nearby organs. In TNM staging this is the same as T4, N0, M0.

Stage 3b
The tumour can be any size. There are NET cells in the nearby lymph nodes. But there are no NET cells in distant organs. In TNM staging this is the same as any T, N1, M0. 

Doctors might call this regional disease.

Stage 4 means the tumour has spread to other parts of the body such as the liver. In the TNM staging, this is the same as any T, any N, M1.   

Doctors might call this metastatic, or advanced, disease.

Treatment

The stage of your NET helps your doctor decide which treatment you need. Treatment also depends on how much the NET cells look like normal small bowel cells. And your general health.

Last reviewed: 
02 Oct 2018
  • Guidelines for the management of gastroenteropancreatic neuroendocrine (including carcinoid) tumours (NETs) 
    J K Ramage and others 
    Gut, 2012
    Vol 61

  • ENETS Consensus Guidelines Update for Neuroendocrine Neoplasms of the Jejunum and Illeum
    B Niederle and others
    Neuroendocrinology, 2016
    Volume 103

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