Grades and stages of neuroendocrine cancer

The tests and scans you have give information about the stage and grade of your cancer. This helps your doctor decide which treatment you need.

A specialist doctor (pathologist ) looks at the cancer cells under a microscope. This tells them:

• what type of cancer you have
• how normal or abnormal the cells look - this is differentiation
• how quickly or slowly the cancer cells are growing - this is the grade

The stage of a neuroendocrine cancer tells you about its size and whether it has spread.

Grading and differentiation

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. They are not like normal neuroendocrine cells at all.

Grading

This is about cell division and growth rate. To describe this, you might hear the terms mitotic rate or Ki67 score or percentage (%). The higher the mitotic rate or Ki67%, the faster the growth.

There are 3 grades of 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 neuroendocrine carcinomas (NECs) are grade 3.

Ki–67 index test

The Ki-67 or mitotic index are ways of describing how many cells are dividing. A specialist doctor (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.

Ki-67 index of 2% or lower

A Ki-67 index of 2% or lower means that fewer than 2 in every 100 cells (2%) are dividing. This is a grade 1 NET (WD NET G1).

Ki-67 index between 3% and 20%

This means that between 3 and 20 cells in every 100 cells (3% and 20%) are dividing. This is a grade 2 NET (WD NET G2).

Ki-67 index higher than 20%

A Ki-67 index of more than 20% means that more than 2 in every 10 cells (20%) are dividing. This is either a grade 3 NET (WD NET G3) or a neuroendocrine carcinoma (PD NEC G3). 

Staging

The stage of a 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 (systems) for staging neuroendocrine cancer. Doctors usually use the TNM system or number system.

TNM system

TNM stands for tumour, node and metastasis:

• T describes the size of the tumour and how far it has grown into nearby tissue
• 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

The staging systems are different depending on where your cancer starts in your body.

Number stages system

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.

This is a brief summary of what the number stages mean for most types of cancer. Your doctor can tell you more about your own cancer stage.

• Stage 1 usually means that a cancer is small and contained within the organ it started in.
• Stage 2 usually means that the tumour is larger than in stage 1 but the cancer hasn't started to spread into the surrounding tissues. 
• Stage 3 usually means the cancer is larger. It may have started to spread into surrounding tissues and there are cancer cells in the lymph nodes nearby.
• Stage 4 means the cancer has spread from where it started to another body organ. For example to the liver or lung. This is also called secondary or advanced or metastatic cancer.

Treatment

The grade and stage of your cancer helps your doctor decide which treatment you need. Treatment also depends on:

• your type of neuroendocrine cancer

• where the cancer starts in your body

• other health conditions you may have