Grades, types and stages of small bowel neuroendocrine cancer
Small bowel neuroendocrine cancers are also called small intestine neuroendocrine cancers. They are cancers that start in the neuroendocrine cells of the small bowel. They might also be named after the part of the small intestine they start in:
- Duodenal neuroendocrine cancers start in the duodenum. This is the top part of the small bowel, which connects to the stomach.
- Jejunal neuroendocrine cancers start in the jejunum. This is the middle part of the small bowel.
- Ileal neuroendocrine cancers start in the ileum. This is the lower part of the small bowel which connects to the large bowel (colon).
Doctors tend to group ileal and jejunal neuroendocrine cancers together. They call these small bowel neuroendocrine cancers.
They sometimes group duodenal neuroendocrine cancers separately from those that start in the ileum and jejunum. Duodenal neuroendocrine cancers can behave quite differently. They group some types of duodenal neuroendocrine cancers with pancreatic neuroendocrine cancers.
Your healthcare team might call your cancer a neuroendocrine neoplasm, or a NEN. This means the same thing as neuroendocrine cancer. There are 2 key groups of small bowel neuroendocrine cancer:
- small bowel
neuroendocrine tumours (NETs 
) - small bowel
neuroendocrine carcinomas (NECs )
A specialist doctor () looks at the cancer cells under a microscope. This tells them:
- whether you have a NET or a NEC
- how fast the cancer cells are growing - this is the grade
The tests and scans you have give information about the of your cancer.
Grading and differentiation
The pathologist looks at a sample of neuroendocrine cancer cells under a microscope.
They look at:
- how abnormal the cancer cells look – doctors call this differentiation
- how quickly or slowly they are dividing and growing – this is grading
Differentiation
This refers to how different the neuroendocrine cancer cells look. This is in comparison to healthy neuroendocrine cells:
- Well differentiated cancers look abnormal. But they still have some similarities to normal neuroendocrine cells.
- Poorly differentiated cancers look very abnormal. There is no similarity to normal neuroendocrine cells.
Grading
This is about cell division and growth rate. To describe this, you might hear the terms mitotic rate or Ki67%. The higher the mitotic rate or Ki67 %, the faster the growth.
There are 3 grades of small bowel neuroendocrine tumours (NETs) – grade 1, 2 and 3:
- Grade 1 cancers grow slowly. They are low grade.
- Grade 2 grow at a moderate pace (between 1 and 3). They are intermediate grade.
- Grade 3 grow rapidly. They are high grade.
All small bowel neuroendocrine carcinomas (NECs) are grade 3.
Types of small bowel neuroendocrine cancer
There are 2 main types of neuroendocrine cancer in the small bowel:
- small bowel neuroendocrine tumours (NETs) – these are well differentiated cancers that can be either slow or fast growing
- small bowel neuroendocrine carcinoma (NECs) - these are poorly differentiated cancers that are fast growing
When neuroendocrine cells become abnormal, they can make and release abnormal levels of . Abnormal hormone production is more common in NETs than NECs. Doctors can group neuroendocrine cancers depending on whether hormone production is disrupted:
- Non-functioning NETs make and release normal levels of hormones.
- Functioning NETs make and release abnormal amounts of hormones.
Doctors also group small bowel cancers depending on which part of the small bowel they are in.
Neuroendocrine cancers that start in the duodenum
These cancers start in the first part of the small bowel. There are different types:
Non functioning NETs are the most common type. Around 90 out of 100 duodenal NETs (around 90%) are non functioning.
Duodenal NETs are often small and there is usually only one tumour. Less than 10 out of 100 duodenal NETs (less than10%) spread to the liver. But it is more common for these cancers to spread to nearby .
Most people don’t have symptoms, and they are diagnosed during tests for another condition.
Doctors sometimes group these cancers with pancreatic neuroendocrine cancer. We have separate pages about gastrinomas, somatostatinomas and non functioning pancreatic tumours.
Neuroendocrine cancers that start in the jejunum and ileum
These cancers start in the middle and end part of the small bowel. Most of these cancers are non functioning NETs.
These NETS are often bigger than 2 cm when they are diagnosed. Some people have more than one tumour.
These NETs have often spread through the muscle layer of the small bowel and into nearby lymph nodes. Around 20 out of 100 of these cancers (around 20%) spread to the liver.
The outlook (prognosis) for these NETs isn’t as good as for some NETs in other parts of the body. This is because they are quite likely to have grown and spread before they are diagnosed.
Small bowel neuroendocrine carcinoma (NEC)
Small bowel neuroendocrine carcinoma (NEC) are rare, fast growing cancers. They can start in any part of the small bowel. They are harder to treat because they have usually spread at diagnosis.
Staging small bowel neuroendocrine cancers
The stage of a small bowel neuroendocrine cancer tells you about its size and whether it has spread. Knowing the stage can help your doctor decide which treatment you need.
You have tests and scans which give some information about the stage of the cancer. Sometimes it’s not possible to be certain about the stage until after surgery.
There are different ways to stage small bowel neuroendocrine cancer. Doctors usually use the TNM system or number system.
TNM stands for tumour, node and metastasis:
- T describes the size of the tumour and how far it has grown through the bowel wall
- 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
Or your doctor might tell you the number stage of your neuroendocrine cancer. Number staging systems use the TNM system to divide cancers into stages. Most types of cancer have 4 stages, numbered from 1 to 4.
The staging systems are different depending on whether your cancer starts in the jejunum and ileum, or the duodenum.
Below we have a simplified description of TNM staging for neuroendocrine cancers of the jejunum and ileum. The staging for dudoenal neuroendocrine cancer is similar, but there are some small differences. In general, it is less likely for a duodenal NET to spread than an ileal or jejunal NET.
Tumour (T)
Tumour describes the size of the cancer. It is divided into 4 main stages. This is a simplified description of the T stages:
T1 means the cancer is no bigger than 1 cm. It has only grown into the inner lining of the small bowel (the mucosa), or into the next layer (the submucosa).
T2 means the cancer has grown into the muscle layer of the bowel wall. Or the tumour is bigger than 1 cm.
T3 means the cancer has grown through the muscle layer and into the first part of the outer lining of the small bowel wall.
T4 means the cancer has grown through the outer lining of the small bowel wall into the tissue layer (peritoneum) covering the organs in the tummy (abdomen). Or it has spread into a nearby organ or structure.
Node (N)
The N stage describes whether the cancer has spread to the lymph nodes .
N0 means there are no lymph nodes containing cancer cells.
N1 means that less than 12 lymph nodes contain cancer cells.
N2 means there are that there are more than 12 lymph nodes containing cancer cells. Or the lymph nodes are larger in size.
Metastasis (M)
The M stage describes whether the tumour has spread to a different part of the body.
M0 means the cancer has not spread to other areas of the body.
M1 means the cancer has spread to other areas of the body, such as the liver.
Treatment
The stage of your neuroendocrine cancer helps your doctor decide which treatment you need. Treatment also depends on the grade of your cancer, and your general health and fitness.
