Stages and grades in cancer- everything you need to know

13th July 2023

Cancer terminology can sometimes be complex, and confusing. In this explainer we talk about cancer staging and grading. We look at what that means, how is it done, and why knowing the stage and the grade of a cancer can help doctors, and patients.

What are stages and grades in cancer?

Staging and grading are two different systems that are used to classify cancer. In a nutshell, staging helps to describe where the cancer is growing, and grading describes what the cancer looks like.

This information is important because it helps doctors and patients know how far a cancer has progressed, and how it is likely to grow in the future.

Doctors may need to carry out several diagnostic tests to gather the staging and grading information they need. This can sometimes take time, and unfortunately it can be a particularly challenging period for patients and their friends and families.

Staging and grading information can also sometimes be quite complex to understand. If you have a cancer diagnosis and are struggling to understand the information you have been given, you can always ask your doctor or another healthcare professional to explain further, and in a way that you understand.

How does cancer staging work?

Doctors will establish the stage of a cancer based on the results of various routine diagnostic tests, including lab tests, biopsies, and imaging tests such as X-rays or MRI scans.

There are many different systems for staging a cancer, but two of the most common systems are the TNM staging system, and the number staging system.




Many cancers can be staged using the TNM system


The T score describes how large the tumour is. This is usually a score from T1 to T4. The higher the number, the larger and more advanced the tumour is.


The N score refers to how far the cancer has spread into surrounding lymph nodes. This number is between 0 and 3, with a higher number meaning the cancer has reached more lymph nodes.


M is the score for cancer spread, or metastasis. This score can be a 0, for no spread, or a 1, meaning it has spread to a different part of the body.

Number staging system

The number staging system groups information from TNM staging and any other useful knowledge into a more easily understandable single number. This number describes how generally advanced a cancer is.

This number is usually between 1 and 4, with the higher number meaning the cancer is more advanced. You might sometimes see these written down as roman numerals (i.e. Stage I, Stage II, Stage III and Stage IV).

A Stage 1 cancer is an early cancer is an early cancer that has not spread, while a Stage 4 cancer is a more advanced and usually larger cancer that has spread to other parts of the body. This type of cancer may need a very different type of treatment to a Stage 1 cancer.

The information that comes from staging a cancer is also a good predictor of outlook. For example we know from research comparing the stage of cancer at diagnosis with the outcome, that cancers diagnosed at an earlier stage are more likely to be successfully treated.  


Are all cancers staged?

Not every cancer is given a stage. For example, the slow growing skin cancer basal cell carcinoma is not usually staged because it very rarely spreads.

The staging system is also less useful for some blood cancers like leukaemia. This is because leukaemia is circulated in the blood, and generally does not form solid tumours. Instead leukaemia may be classed as ‘acute’ (more aggressive), or ‘chronic’ (slower-growing).

Brain tumours are also not generally staged, as primary brain tumours (which start inside the brain) do not tend to spread outside of the brain and spinal cord. Instead, brain tumours usually receive a grading, from 1 to 4.

How does cancer grading work?

Doctors usually grade a cancer by looking at a sample of cancer and investigating exactly what the cells look like. The aim is to assess how different they look compared to healthy cells. 

Cancerous cells usually have much more disorganised shape and structure than healthy cells, and their internal parts can look different. For example an important part of the cell called the nucleus can look much larger and darker in a cancer cell, compared to a healthy cell.

The doctor then gives the cancer a grade based on how different it looks to healthy cells. This is often as a score between 1 and 3 (or sometimes 4):

  • ‘Low-grade’ cancers (Grade 1) still look quite similar to healthy cells, with only small changes.
  • ‘Intermediate-grade’ cancers (Grade 2) have more obvious changes compared to healthy cells.
  • ‘High-grade’ cancers (Grade 3 or 4) look very different to healthy cells. They have very obviously altered structures and organisation.

Knowing the grade of a cancer can tell doctors how the cancer is likely to behave. The higher the score, the more aggressive and faster growing the cancer is likely to be. It is also possibly more likely it is to spread. Higher-grade cancers tend to have a poorer outlook than low-grade cancers, and will usually require different treatment.




When are cancers graded?

Grading a cancer usually requires obtaining a sample of cancer cells. Sometimes this is done by biopsy, where a small part of the cancer is taken for initial examination before any treatment happens. Or if the cancer is being treated by surgery, sometimes a sample of the cancer removed during surgery is studied under a microscope to find the grade. Doctors can then use this information to decide whether further follow-up treatment is needed.

How is research changing how we stage and grade cancer?

Diagnosing a cancer is a bit like painting a picture- the information that comes from staging and grading adds vital detail to the overall image. As research continuously helps to improve our understanding of cancer, this in turn helps to make grading and staging systems more accurate. Diagnosis then becomes easier, quicker, and more detailed, and the picture becomes even more clear.

Help for families with Fanconi anaemia

This is why work by researchers like Professor Kevin Hiom is so important. Thanks to vital Curestarter support, Professor Hiom and his team discovered new genetic information about a rare condition called Fanconi anaemia. Children with Fanconi anaemia may have developmental disabilities, and are also more likely to develop cancer. An early and accurate diagnosis is really important in helping doctors and families understand how to manage the condition.

The information discovered by Professor Hiom and his team is now helping to improve the diagnosis process for Fanconi anaemia, and making a real difference to some of these families.

Improving treatment options for difficult to treat cancers

Understanding the molecular and genetic profile of a cancer can add even more detail to the picture, and this information is increasingly becoming an important part of the staging, grading, and diagnosis process.

The molecular information for each cancer can be very specific. It sometimes even differs between people with the same type of cancer. It helps to explain why some cancers respond to better to certain treatments while others do not, and is increasingly being used to help guide some treatment choices. This approach is called ‘personalised treatment’, and it is cutting-edge.

Right now, Curestarter-funded researchers around the world are busy discovering new molecular information about cancer, and working out how to use that information to improve diagnosis and personalised medicine.  

Researchers like Dr Carsten Hansen and his team in Edinburgh, who thanks to your support, have been studying the molecular profile of the asbestos-related lung cancer pleural mesothelioma. They have found that some types of pleural mesothelioma have certain genetic mutations that could mean they respond to different treatments. This is an important first step in the search for new ways to improve diagnosis and treatment for patients with this difficult to treat disease.

It’s only through your ongoing support of life-changing research like this that our researchers can continue to find new ways to detect and diagnose cancer and cancer-related conditions earlier, and ultimately develop more effective treatments. Thank you Curestarters!



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