Grades, types and stages of stomach neuroendocrine cancer
Stomach neuroendocrine cancers are rare stomach cancers. They start in the 
of the stomach.
Your healthcare team might call them stomach neuroendocrine neoplasms, or stomach NENs. This means the same thing as stomach neuroendocrine cancer. There are 2 key groups of stomach neuroendocrine cancer:
- stomach neuroendocrine tumours (stomach NETs)
- stomach neuroendocrine carcinomas (stomach NECs)
There are also different sub-types of:
- stomach NETs - these are types 1, types 2 and type 3
- stomach NECs - these are small cell and large cell stomach NEC
A specialist doctor () looks at the cancer cells under a microscope. They report:
- how abnormal the cells look (differentiation)
- how quickly or slowly the cancer cells are dividing and growing (the grade)
This helps to tell them whether you have a NET or a NEC.
The stage of a neuroendocrine cancer tells you its size and whether it has spread.
The tests and scans you have give information about the type, stage and grade. This helps your doctor decide which treatment you need.
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
Your doctor uses the differentiation to diagnose you with one of the following:
- stomach neuroendocrine tumour (stomach NET) – these are well differentiated cancers
- stomach neuroendocrine carcinoma (stomach NEC) – these are poorly differentiated cancers
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.
The Ki-67 or mitotic index are ways of describing how many cells are dividing. The pathologist counts the number of cancer cells that have started to divide into 2 new cells (mitoses) under a microscope. And a special stain measures the Ki-67 value.
Your doctor might tell you the number of cells that are dividing (number of mitoses), or you may see this on your pathology report. This helps your doctor decide which treatment you need.
There are 3 grades of stomach neuroendocrine tumours (NETs) – grade 1, 2 and 3:
- Grade 1 cancers grow slowly. They are low grade. They have a Ki-67 index of 2% or lower. This means that fewer than 2 in every 100 cells (2%) are dividing.
- Grade 2 cancers grow at a moderate pace (between grade 1 and 3). They are intermediate grade. They have a Ki-67 index between 3% and 20%. This means that between 3 and 20 cells in every 100 cells (3% and 20%) are dividing.
- Grade 3 cancers grow rapidly. They are high grade. They have a Ki-67 index higher than 20% This means that more than 20 in every 100 cells (20%) are dividing.
All stomach neuroendocrine carcinomas (NECs) are grade 3.
Types of stomach neuroendocrine tumours (NETs)
Stomach NETs are more common than stomach NECs. There are 3 main types of stomach NET: Type 1, 2 and 3.
Type 1
The most common type of stomach (gastric) neuroendocrine tumours is type 1. Between 70 and 80 out of 100 stomach NETs (between 70 - 80%) are type 1.
They are often linked to a condition called chronic s. This causes inflammation of the stomach cells, which leads to problems with stomach acid production. People with type 1 stomach NETS can have a higher than normal level of the hormone .
It is rare that type 1 stomach NETs cause symptoms. So most people are diagnosed with it during tests for other problems.
These stomach NETs are usually low grade and well differentiated. It’s rare that they spread (metastasise). They are usually small. And there is often more than one tumour, all of which are small.
The outlook (prognosis) for type 1 stomach NETs is excellent.
Type 2
Type 2 stomach NETs are much less common than type 1. Around 5 out of 100 stomach NETs (around 5%) are type 2.
Type 2 stomach NETs are linked to a rare condition called Zollinger Ellison Syndrome (ZES). ZES is the name given to the collection of symptoms caused by high levels of the hormone gastrin. The gastrin levels are high because of a rare type of tumour called a gastrinoma. Gastrinomas makes large amounts of gastrin. They usually develop in the small bowel or pancreas.
Type 2 stomach neuroendocrine cancers are also linked to another inherited syndrome called ).
It’s rare for type 2 stomach NETs to cause symptoms. The cancers are usually low grade and well differentiated. They are often small and there is usually more than one tumour.
There is a slightly higher risk of type 2 NETs spreading than type 1. Between 10 and 30 out of every 100 type 2 tumours (between 10 and 30%) spread to another part of the body.
The outlook (prognosis) for type 2 stomach NETs is usually good.
Type 3
Around 15 out of every100 stomach NETs (around 15%) are type 3.
There is usually one, larger tumour. Type 3 is more likely to be high grade than type 1 and 2 NETs. There is also a higher risk of type 3 NETs spreading. Over 50 out of 100 type 3 stomach NETs (over 50%) spread to another part of the body.
The outlook (prognosis) for type 3 stomach NETs is less good than types 1 and 2.
Other types of stomach NET
How doctors group and classify cancers changes all the time. Some experts think that type 3 stomach NETs should be further divided into subtypes. This would depend on how well or poorly differentiated the cancer cells look.
Types of stomach neuroendocrine carcinoma (NEC)
Stomach neuroendocrine cancers (NECs) are poorly differentiated cancers. This means the cancer cells look very different to normal neuroendocrine cells. They are fast growing and have often spread to other parts of the body at diagnosis.
They are less common than stomach NETs. Around 6 – 21% of stomach neuroendocrine cancers are NECs. There are different types of stomach NEC:
- small cell stomach NEC
- large cell stomach NEC
You can also get neuroendocrine cancer cells mixed in a tumour with a different type of cancer. Doctors call this MiNEN or mixed cell carcinoma.
Unfortunately, stomach NECs are harder to treat than NETs, so the outlook (prognosis) for stomach NEC isn’t good.
Staging stomach neuroendocrine cancer
The stage of a stomach 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 stomach neuroendocrine cancer. Doctors usually use the TNM system.
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
Number staging
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.
Below we have a simplified description of TNM staging for stomach neuroendocrine cancer.
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 stomach (the mucosa), or into the next layer (the submucosa).
T2 means the cancer has grown into the muscle layer of the stomach wall. Or the cancer 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 stomach wall.
T4 means the cancer has grown through the outer lining of the stomach 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 there are neuroendocrine cancer cells in the nearby lymph nodes.
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 for stomach neuroendocrine cancer
Treatment depends on what type of stomach neuroendocrine cancer you have. Treatment also depends on:
- the stage of the stomach neuroendocrine cancer
- where the cancer is
- your health and general fitness
