What cancer grading is:

You may hear your doctor talk about the grade of your cancer. Tumour grade describes a tumour in terms of how abnormal the tumour cells are compared to normal cells. It also describes how abnormal the tissues look under a microscope.

The grade gives your doctor some idea of how the cancer might behave. A low grade cancer is likely to grow more slowly and be less likely to spread than a high grade one. Doctors can't be certain exactly how the cells will behave. But the grade is a useful indicator.

Tumour grade is sometimes taken into account as part of cancer staging systems. The stage of a cancer describes how big the cancer is and whether it has spread or not.

Common grading systems

Some types of cancer have their own grading systems but generally there are 3 grades. They are described as

Grade 1 – The cancer cells look very similar to normal cells and are growing slowly

Grade 2 – The cells look unlike normal cells and are growing more quickly than normal

Grade 3 – The cancer cells look very abnormal and are growing quickly

Some systems have more than 3 grades.

GX means that the grade can't be assessed. It is also called undetermined grade.

Differentiation

Types of staging systems

Another way of describing the cells is by how differentiated they are. Differentiation refers to how well developed the tumour cells are and how they are organised in the tumour tissue. If the cells and tissue structures are very similar to normal the tumour is called well differentiated. These tumours tend to grow and spread slowly.

In poorly differentiated or undifferentiated tumours the cells look very abnormal and the cells are not arranged in the usual way. So the normal structures and tissue patterns are missing. These tumours may be more likely to spread into surrounding tissues or to other parts of the body.

Cancer grade and treatments

Cancer treatment teams take into account the tumour grade and other factors such as the stage of a cancer, the person's age and their general health. This helps them to predict the likely outcome of the person's cancer and decide on the best treatment. Generally, a lower tumour grade indicates a better outlook. A higher grade cancer may grow and spread more quickly and may need faster or more intensive treatment.
For some types of cancer the grade is very important in planning treatment and predicting outlook. These include soft tissue sarcoma, primary brain tumours, and breast and prostate cancer.
It is important to talk to your doctor for specific information about tumour grade and how it relates to your treatment and the possible outcome.