Why cancers are staged
The stage of a cancer tells the doctor how far it has spread. The tests and scans you have when diagnosing your cancer give some information about the stage.
Treatment is often decided according to the stage of a cancer. Your doctor may not be able to tell you the exact stage of your cancer until after your surgery.
There are different ways of staging cancers. The two main ways are the TNM system and number system.
TNM stands for Tumour, Node, Metastasis. This system describes the size of a primary tumour (T), whether there are lymph nodes with cancer cells in them (N) and whether the cancer has spread to a different part of the body (M).
Tis (carcinoma in situ) is very early stage pancreatic cancer, which hasn't spread. It is uncommon for pancreatic cancer to be diagnosed this early.
T1 means the tumour is inside the pancreas and is 2cm or less in any direction.
It is divided into :
- T1A means the cancer in no more than 0.5cm in size in any direction
- T1B means the cancer is more than 0.5cm but no more than 1cm in size in any direction
- T1C means the cancer is more than 1cm but no more than 2cm in size in any direction
T2 means the cancer is more than 2cm but no more than 4cm in size in any direction.
T3 means the cancer is more than 4cm in size.
T4 means the cancer has grown outside the pancreas, into the nearby large blood vessels.
Node (N) describes whether the cancer has spread to the lymph nodes.
N0 and N1 stages
N0 means there are no lymph nodes containing cancer.
N1 means there are 1 to 3 lymph nodes that contain cancer cells.
N2 means that there is cancer in more than 4 lymph nodes.
Cancer that has spread to the lymph nodes means the cancer is more likely to have spread further than the pancreas.
Metastasis (M) describes whether the cancer has spread to a different part of the body.
M0 and M1 stages
M0 means the cancer has not spread into distant organs such as the liver or lungs.
M1 means the cancer has spread to other organs.
The stage of your cancer helps your doctor to decide which treatment you need. Treatment also depends on:
- your type of cancer (the type of cells the cancer started in)
- where the cancer is
- other health conditions that you have
The stage of the cancer and these other factors can also give an idea of your outlook (prognosis).
Grades of pancreatic cancer
The grade of the cancer means how normal or abnormal the cells look under the microscope. It can give some idea of how quickly or slowly a cancer might grow or spread.
Grading for exocrine pancreatic cancers
Exocrine pancreatic cancers include the most common type called adenocarcinoma. Grading for these cancers uses a scale from G1 (low grade) to G3 or sometimes G1 to G4.
G1 cancers look the most like normal cells and have the best outlook.
G3 or 4 cancers have very abnormal cells. They are called high grade and are likely to grow or spread more quickly.
Grading for pancreatic neuroendocrine tumors (NETs)
The NET grading system is a little different. This system looks at how normal or abnormal the cells look and also at how many cells are in the process of dividing. The pathologist counts cells that have started to split into two new cells (mitoses) under a microscope. They use a test called a Ki-67 test to see how many cells are almost ready to start splitting.
Based on these tests, NETs are divided into 2 groups.
Well differentiated NETs
These are low grade and intermediate grade tumours that have 20 or fewer mitoses and a Ki-67 index of 20% or lower.
Poorly differentiated NETs
Tumours are high grade and have more than 20 mitoses or a Ki-67 index of more than 20%. These are also called neuroendocrine carcinomas, and they often grow and spread quickly.