Grades, types and stages of small bowel neuroendocrine cancer

What are small bowel neuroendocrine cancers?

Small bowel neuroendocrine cancers are also called small intestine neuroendocrine cancers. They are cancers that start in the neuroendocrine cells of the small bowel.

Read about the difference between NETs and NECs

Grading small bowel neuroendocrine cancers

The pathologist looks 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. These are neuroendocrine tumours (NETs).

• Poorly differentiated cancers look very abnormal. There is no similarity to normal neuroendocrine cells. These are neuroendocrine carcinomas (NECs).

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 cancers grow slowly. They are low grade.

• Grade 2 grow at a moderate pace (between 1 and 3). They are intermediate grade.

• Grade 3a grow rapidly. They are high grade.

All small bowel neuroendocrine carcinomas (NECs) grow rapidly and are grade 3b.

Read more about grading neuroendocrine cancer

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 carcinomas (NECs) - these are poorly differentiated cancers that are fast growing

When neuroendocrine cells become abnormal, they can make and release abnormal levels of ​hormones​ . 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. 

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).

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 ​lymph nodes.

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.

Read more about pancreatic neuroendocrine cancers

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. 

Read more about neuroendocrine carcinomas (NECs)

The stages of 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.

Treatment for small bowel neuroendocrine cancer

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.

You can find out about treatment here