Grades of pancreatic NENs and Ki-67 index test

Pancreatic neuroendocrine neoplasm (NEN) is the umbrella term for Neuroendocrine tumours (NETs) and Neuroendocrine carcinomas (NECs). 

Grading and the Ki-67 index gives your doctor an idea of how quickly the pancreatic neuroendocrine neoplasm (NEN) might grow and whether it is likely to spread. This helps your doctor decide which treatment you need.

Doctors use the same grading system for all types of pancreatic NENs.

What is the grade of a pancreatic NEN?

The grade of a pancreatic NEN tells you how much the cancer cells look like normal cells under the microscope. It gives your doctor an idea of how the tumour might behave and whether it is likely to spread. 

There are different ways to grade pancreatic NENs. In the UK, doctors use a system created by the World Health Organisation (WHO). The 2019 WHO grading system divides pancreatic NENs into 2 groups:

• Well differentiated neuroendocrine tumour (WD NET), which can be subdivided into grade 1, grade 2 or grade 3 depending on the number of cells which are dividing.
•  Poorly differentiated neuroendocrine carcinoma (PD NEC), which are always grade 3.

NET
The cells look very like normal cells. Tumours are usually slow growing and less likely to spread. They are also called low grade or well differentiated tumours.

NEC
The cells look very abnormal. They tend to grow quickly and are more likely to spread.

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 NEN 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). 

Treatment

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

• the type of pancreatic NEN you have
• where the cancer is
• other health conditions you may have